Diving Straight into Photographic Rendering

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Photographic Rendering with V-Ray for SketchUp

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An all-inclusive guide to creating a photo quality V-Ray render for SketchUp with this book and ebook

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by Brian Bradley | March 2014 | Open Source

In this article by Brian Bradley, the author of Photographic Rendering with V-Ray for SketchUp, discusses V-Ray in SketchUp as it guides us through with the use of many key areas in the render engine, all of which need to be utilized by an artist if they want to produce photographic renders using V-Ray.

(For more resources related to this topic, see here.)

Lighting that sets the mood!

While a good composition gives us a solid foundation on which to build a photographic render, if we try to render a scene that has no lighting, well let's just say the end results will fall quite a way short of those desired.

The brilliant thing about lighting a scene with V-Ray in SketchUp is that a complete day-lighting system that consists of both the Sun and Sky elements is, by default, set up and ready to render with as soon as we start creating geometry in the scene. For newer users, this can obviously help tremendously when it comes to getting up and running with the software.

Controlling the placement of the Sun is extremely easy as we simply need to make use of SketchUp's built-in shadow controls, wherein we set the month of the year along with the time of day and time zone, and then we can render. What we instantly get is natural-looking daylight without having to do anything at all!

Better still is the fact that V-Ray also sets up a basic indirect (or global) illumination system for us automatically. This means we can even render interior Arch Viz shots right out of the box without having to do any extra set up work beyond, of course, getting our geometry created and then positioned in the scene.

Global illumination is a general name for a group of algorithms used in 3D computer graphics that are meant to add more realistic lighting to 3D scenes. Such algorithms take into account not only the light which comes directly from a light source (direct illumination), but also subsequent cases in which light rays from the same source are reflected by other surfaces in the scene, reflective as well as non-reflective (indirect illumination). The source of this content is Wikipedia.

To look at the kind of renders we can get from V-Ray without doing any real lighting setup at all, either continue to work with your current scene or open up the Ch01_03_Lighting.skp file from your Exercise_Files folder, if you prefer to work with the same scene as I will be using.

Stepping through the render process

The scene or camera angle we are using here (Scene 2) has been deliberately chosen to help us properly evaluate the quality and level of lighting that we are getting in our scene. It can do this because it affords us a full view of the environment.

With our camera view set to Scene 2, let's take a render by clicking the render button on the V-Ray toolbar. Once the initial translation phase is complete, V-Ray opens up its own frame buffer window and starts the rendering phase.

One of the very nice features of V-Ray Version 2.0 is the fact that translation times in scenes are now significantly faster (in the vast majority of cases) than rendering the same scene in V-Ray Version 1.49.

The first activity we see in the frame buffer window will be V-Ray's indirect illumination calculations. First of all, the light cache and then the irradiance mapping engines calculate the level of illumination and light bounce requirements for the scene. This is based on the parameters set up in the V-Ray option editor and the materials applied through the materials editor.

Irradiance mapping and light cache are the two indirect illumination engines set up by default in V-Ray Version 2.0 for SketchUp.

The final part of this process is the rendering of the image itself. In this instance, what we get, as we no doubt could discern from the GI calculations, is way too dark for the type of bright and airy feel in the interior that we are looking for. This brings us to a critical aspect of lighting in V-Ray, exposure!

Using V-Ray's physical camera model

Another default aspect of the V-Ray setup in SketchUp is that it makes use of a physical camera model for rendering. This means that real-world parameters such as shutter speed, F numbers (or F stops), and ISO (or film speed) values are used to control various aspects of the render, such as exposure, motion blur, and depth of field.

Basically, if we understand how to control these elements on a real-world camera, be it film or digital, then we already have a big head start when it comes to rendering using the V-Ray physical camera model. To access the physical camera controls, we need to revisit the V-Ray toolbar and click on the option editor button once more.

Then, if we open the Camera rollout, you can see in the following screenshot that we now have access to a wealth of camera controls and parameters. As we have already noted that our render is quite a bit darker than desired, the controls we are interested in would be those capable of affecting the exposure levels, which would be as follows:

  • Shutter Speed
  • F Number
  • Film Speed (ISO)

As a general rule, I prefer to handle exposure levels using only the film speed value as much as I possibly can. This is due to the fact that it is the only one of the three controls in what is often referred to as the exposure triangle that isn't used to control some other aspect of the physical camera model. Shutter speed is also used to control motion blur while the F number (or F stop) value will typically be the control mechanism for any Depth of Field (DOF) effects in our render.

To get some nice brightness levels in this instance, let's adjust the film speed or ISO value and set it to 1200. Taking another render by hitting the render button on the far right of the V-Ray frame buffer's top toolbar will show us that our illumination levels are now much more appropriate for the bright, airy feel we want to create.

The higher the ISO number we use in a render, the more sensitive V-Ray becomes to light, thereby producing a brighter final image. Unlike the ISO setting on a digital camera, we can increase this value as much as we like in V-Ray without the fear of introducing artifacts or noise into our rendered images.

Global illumination controls

The next aspect of our lighting setup that needs a little attention is the quality of the indirect illumination solution. At this moment, we can see quite a bit of dark splotching on our nice clean geometry. This often happens when we work with scenes that present a little bit of a challenge to the indirect illumination engines, which, of course, interiors nearly always do. Couple this with the reasonably low-quality default settings that V-Ray sets up, and we get splotches or noise patches in our render.

To clean this up a little, let's perform the following steps:

  1. Jump into the Irradiance map rollout in the option editor, and in the Basic Parameters section, set the minimum and maximum rate values to -2 and -1 respectively.
  2. We can also increase the HSph.subdivs value to 125 and the Interp.samples value to 35.
  3. Next, we can jump into the Light cache rollout and increase the Subdivs (or subdivisions) value to 1200.

If we take another render by hitting the button on the toolbar, we should see a marked improvement in the level of splotchiness present in the image; not that every trace of it will be gone, mind you. When working with interior scenes, creating completely noise-free Global Illumination (GI) renders can prove to be quite costly in terms of the time it takes to render the final image.

What we often have to aim for then is a situation that would generally be considered free enough of noise to be called an acceptable final solution. One reason why we can often get away with this is the fact that once materials get applied to the geometry, any slight levels of splotchiness still found in the scene tend to oftentimes just blend into the materials themselves.

We do need to bear in mind that every increase in quality settings inside a render engine, such as those we have just applied to the indirect illumination controls, will result in a corresponding increase in the time it takes for the render to complete! This is typically referred to as the speed verses quality conundrum.

Photographic Rendering with V-Ray for SketchUp An all-inclusive guide to creating a photo quality V-Ray render for SketchUp with this book and ebook
Published: March 2014
eBook Price: $29.99
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Materials that make us believe!

This, of course, leads us nicely onto the subject of creating believable materials for our models. Because this is just a quick start exercise and we will be devoting an entire article to the development of some very specific materials in V-Ray, we will deal with just two things here. First, we will demonstrate how to apply existing materials to various geometry elements in the scene. And second, we will walk through the creation of a new floor material just to get a feel of how the V-Ray standard material works.

To get started, we can either continue with our current file or open up the Ch01_04_Materials.skp file from the downloadable Exercise_Files folder. This file essentially picks up where our lighting tweaks have left off. Let's introduce ourselves straight away to the V-Ray material editor by going back to the V-Ray toolbar and clicking on the M (for material editor) button. This, of course, will open up the editor window for us.

Looking in the Materials List section, you can see that we have a material named Basic. This is the plain grey material currently assigned to all the geometry in the scene. As we want to alter this arrangement, we need to briefly cover the setup or current state of geometry in the scene.

What I am referring to is the fact that everything in our scene at this moment in time has been turned into either a group or a nested group. This, for those who may be unfamiliar with SketchUp, will affect how we go about applying materials to the geometry. For instance, with one of the shelf objects selected, I can right-click on Shelves material in the Materials List section and choose the Apply Material to Selection option.

The selected material is then applied to that geometry. However, if I select a geometry group such as the main building itself, those same steps will no longer work and the material application would fail.

To apply a material to this type of geometry, we need to perform the following steps:

  1. Double-click on the main building geometry to open up the group.
  2. In the Edit menu, use the Select All command.
  3. Right-click on a material in Materials List, such as Building Paint, and then choose the Apply Material to Selection option.

Once a group is open, we close it by using the Close Group/Component command from the Edit menu.

We need to follow a similar process when working with nested groups. Applying a material directly to a nested group such as our table won't work. However, we can perform the following steps to attain the desired result:

  1. Double-click to open the nested hierarchy.
  2. Left-click to select one of the groups.
  3. Select a material from the Materials List section.
  4. Right-click and choose Apply Material to Selection.

The material should then apply just fine. If it doesn't, we will need to perform the following extra steps inside the nested group:

  1. Double-click on one of the nested groups.
  2. Use the Select All command from the Edit menu.
  3. Select a material from the Materials List section.
  4. Right-click and choose Apply Material to Selection.

This may seem like a clunky way to get things done, especially if we are coming to SketchUp from other 3D applications. However, once the process becomes familiar to us, it really does become second nature and flows quite freely.

Now that we understand the process of applying materials, go ahead and see if you can get the named textures in Materials List applied to their related scene objects. This is a good way to get some practice at working with the preceding outlined steps.

To keep ourselves moving forward, let's run through the creation of a material of our own. This is what we will use to texture the floor in our scene.

Do keep in mind that we already have a Floor Material in our Materials List that can be used as a reference at any point if you should get a little stuck.

Creating the floor material

To move forward, we can either continue with our current file or open the Ch01_05_FloorMat.skp file from our Exercise_Files folder.

The first thing we want to do here is create a new V-Ray standard material for ourselves. So, let's perform the following steps in Materials List:

  1. Right-click on either the Scene Materials label itself, or with the Scene Materials label selected, right-click on an empty area of the Material List panel.
  2. In the pop-up menu, hover over the Create Material option and select the Standard material from the flyout.
  3. Then, we need to locate the newly created label named DefaultMaterial in the Materials List.
  4. Right-click on it and choose the Rename Material option from the pop up.
  5. In the Rename Material window that opens up, call the new material My Floor and click on OK.

Of course, we will want to assign this material to the floor geometry straight away. Our new material is currently using grey for its diffuse color, making it the same as the already assigned basic material; we will avoid any potential confusion by changing our new material's diffuse color to something that will enable us to tell them apart.

To change this to something more recognizable, let us perform the following steps:

  1. In the Diffuse rollout of our My Floor material, click on the diffuse color swatch.
  2. In the Select Color dialog box, choose a color that would be very noticeable in the scene, such as the burnt orange I will create here. Let's use the HSV settings of HSV 12, 240, and 218.
  3. Then, enable the select tool from the Large Toolset toolbar.
  4. Triple-click on the floor geometry in the scene to ensure that it is all selected, or we could double-click and then use the Select All command from the Edit menu.
  5. Right-click on the My Floor material name in the editor and choose Apply Material to Selection from the pop up.

If our burnt orange color appears in the viewport, we know that we have successfully applied this new material to the geometry; not that we will leave it set at burnt orange of course. In fact, we won't actually use the diffuse color swatch at all. Instead, we will make use of a number of bitmap or image files to help give our floor material a little more visual interest. To do this, perform the following steps:

  1. Click on the map button (m) to the right of the diffuse color swatch.
  2. From the drop-down list that appears under the Preview button, select the TexBitmap option.
  3. In the Open Bitmap File dialogue box that appears, navigate to your downloaded Exercise_Files folder, and from the Textures subfolder, click to open the Floor.bmp file.

  4. Then, click on OK to close the texture editor window.
  5. And finally, let's lower the diffuse map's overall level of contribution by setting the spinner value to 0.25.

We should now see our bitmap texture appear in the SketchUp viewport. At this moment, however, the default UV mapping coordinates are causing the bitmap to tile way too much for my liking. To rectify this, we need to use the controls found in SketchUp's own Materials editor.

To access that, let's perform the following steps:

  1. Click on the Paint Bucket tool over on the SketchUp toolbar.
  2. In the SketchUp Materials editor window, click on the Edit tab.
  3. In the Edit tab, we have width and height controls that appear just below the image naming field. Click on the Lock/Unlock aspect ratio button that appears next to these fields.
  4. This will allow us to set different values for each of the dimensions.

  5. Enter values of 3.00 meters for the width and 2.30 meters for the height.
  6. Close the SketchUp Materials editor.

We should be able to see the difference this has made straight away in the viewport.

Adding surface properties

Next, we need to apply some parameter changes that will help us add some realism to our floor material. The first thing that we need is some reflections. To do this, we need to specifically add reflection controls to our V-Ray standard material.

Although V-Ray Version 2.0 in SketchUp, just like other applications such as 3ds Max and Maya, now has a V-Ray Material that has all of the relevant parameter sections such as reflection and refraction set up and ready to work.

In the V-Ray material editor, let's perform the following steps:

  1. Right-click on the My Floor material.
  2. In the pop-up menu, hover over the Create Layer option, and from that flyout, choose the Reflection option.
  3. Next, in the General area of the Reflection rollout, set the spinner next to the reflection color swatch to a value of 0.25. (We can double-click and type the values in any of these fields if we want.)

    Then, we need to click on the map button (m) next to the reflection color swatch. In the texture editor parameters window that appears, click on the map button (m) for the Perpendicular controls.

  4. In the drop-down list below the Preview button, choose the TextBitmap option.
  5. And, in the Open Bitmap File dialog box that appears, navigate to Exercise_Files | Textures and once more choose the Floor.bmp file.
  6. Finally, click on OK in the two open dialogs to go back to the materials editor window.

Placing the bitmap in the perpendicular channel here will give us some nice variation in the reflection intensity, which will automatically make things feel a little more natural. Next, we need to add some breakup to those reflections. So, in the Reflection rollout of the My Floor material, go to the Glossiness section and set the Hilight and Reflect values to 0.85.

Then, as a finishing touch, we can add a bit of a textured feel to the floor along with extra breakup by adding a subtle bump map to the material. To do that, let's perform the following steps:

  1. Open up the Maps rollout at the bottom of the material controls.
  2. Put a check in the Bump option, and at the same time, set its spinner value to 0.1.
  3. To add a map for the bump effect, click on the map button and select the TextBitmap option from the drop-down list beneath the Preview button.
  4. In the Open Bitmap File window that appears, navigate to Exercise_Files | Textures and choose the Wall_Stucco_Bump.bmp file.
  5. In the UVW section at the bottom of the texture editor controls, set u and v Repeat values to 4 and then click on Ok to exit the editor.

We can now take a render and see how things are looking by coming up to the V-Ray toolbar and clicking on the render button. Hopefully, what you have should look just like the following render:

We are closing in on a decent quick start image here. However, before we go ahead and create our final output render settings, let's just see how we can tweak things a little, now that all of our materials are fixed in place.

Final setting tweaks!

One area that I will want to address are the super bright whites that we are currently getting inside the render. You can find these by right-clicking on the image inside the V-Ray frame buffer, which should pop up a Pixel information dialog that contains RGB data readouts for varying image bit depths.

V-Ray can do this because, by default, renders inside the frame buffer are stored at the highest bit depth possible using floating point values.

The one we are specifically interested in would be the Color (float) option. Whenever all three numbers in this readout go above the value of 1, which is pure white in floating point terms, then we know that what we are looking at is one or more super bright pixels in the image.

Sometimes, we can use these to good effect in our renders, especially when it comes to using the new Lens Effects feature of V-Ray Version 2.0. At other times, however, the burnout these super bright pixels cause, particularly in areas where direct light falls on an already bright texture such as our white walls, can be extremely undesirable. This means that it will always be useful to know which V-Ray tools can be used to help deal with this. One set of such tools would be the color mapping controls.

However, before we go ahead and make any changes, I am going to open up the Ch01_06_Tweaks.skp file from the Exercise_Files folder, which again picks up from where we currently have the scene. (Again, feel free to continue on using the current file, if you prefer.)

To deal with our super brights, let's perform the following steps:

  1. Reopen the option editor by using the button on the V-Ray Main toolbar.
  2. Inside the dialog, we want to open up the Color Mapping rollout and select the Exponential option from the Type drop down.
  3. We also need to set Bright Multiplier here to a value of 1.0 instead of the default 0.8.

This simple change in the color mapping type will prevent any of the RGB values in our image from climbing above a value of 1. Another effect of this color mapping change is that our rendered image will become a little less bright and the RGB values of our extremely blown-out sky will drop to levels below 1, meaning that we can now see a little bit of blue in there!

Another lighting tweak we might want to make at this point is in connection with the current positioning of the direct sunlight in our view. At this moment in time, the sunlight coming through the skylights is creating one or two bright spots on the left side wall, which are looking a little messy and may need cleaning. We can do that by basically shifting the Sun a little in our scene. To do that, we need to perform the following steps:

  1. Open up SketchUp's Shadows control dialog from the Window menu.
  2. Then, set the time of day to 11.10 a.m. by using either the spinner or clicking in the text field and typing.

    In order to apply this change to all of the scene views, we will of course need to select each one of them in turn and repeat this step. Remember that in order to have this change fixed in the scene, we will need to right-click on the scene tabs and use the Update option.

With that done, we will not only eliminate those distracting highlights, but we will actually create another element of symmetry in the shot in which the spots of light now fall on either side of the window opening.

One element that seems to be a little bit lacking in the scene would be occlusion or contact shadows. We may particularly expect to see these in corner areas of the room, especially the shelving recesses. At this point, we ideally want to add them without creating an extra image element that would need to be composited in another application. In this instance, we will choose the easiest route available to accomplish this and enable V-Ray's ambient occlusion option by following the given steps:

  1. With the V-Ray Options dialog open, go to the Indirect Illumination rollout.
  2. In the Ambient Occlusion section, check the On box.
  3. Set the radius amount to 8.5.
  4. As we want the effect to be fairly subtle, let's set Amount to 0.35.

With our lighting tweaks in place, a final, slightly distracting element that we may want to tackle could be the material we have applied to the shelves in the scene. I am not entirely convinced that what we have created sits well in the scene. So, I would like to experiment a little and try applying the same material that we are using for our overhead panels.

To do that, follow the given steps:

  1. Select all of the shelf objects in the scene.
  2. Open up V-Ray material Editor.
  3. Right-click on the Overhead Panel material.
  4. From the pop up, choose the Apply Material to Selection option.

Summary

Let's summarize the elements of photographic rendering that we have very quickly touched in this article.

As with any construction project, the crafting of a photographic render requires that we start with a solid foundation. In this instance, that means getting our basic composition in the scene right before we move on to using the tools found in the render engine itself. Solid compositional principles such as thirds, leading lines, and points of view should be considered and possibly even tried out at this phase of the project.

Once we have that in place, we can then move onto using V-Ray tools to craft a lighting setup in the scene that creates an appropriate mood for us; then, build and apply materials to scene geometry that have believable physical properties associated with them.

Add to this mix global illumination, exposure control, and then finally our finished render and output quality control settings. Now, we have a recipe for successfully creating photographic renders with V-Ray.

Resources for Article:


Further resources on this subject:


Photographic Rendering with V-Ray for SketchUp An all-inclusive guide to creating a photo quality V-Ray render for SketchUp with this book and ebook
Published: March 2014
eBook Price: $29.99
Book Price: $49.99
See more
Select your format and quantity:

About the Author :


Brian Bradley

Brian Bradley is a self-taught 3D artist and Training Author who started experimenting with creative software and 3D applications back in 1993. By the mid 90s, he was running his own small multimedia business working on projects as diverse as corporate logos, graphic design for clothing and vehicles, as well as developing full product and architectural visualization projects.

In 2007, he turned the attention of his family-run studio toward full-time production of CG Training, focusing initially on 3ds Max along with the mental ray and V-Ray render engines. In 2012, he joined the ranks of Training Authors producing course for the lynda.com online training library, producing (among others) V-Ray-based courses for 3ds Max, Maya, and of course, SketchUp.

Recently, Brian and his team have completed a revamp of the vrayelite.com website that they run and they plan to work at slowly but surely expanding both the level and quality of training and content that it houses.

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