Creating a Lamborghini Murcielago

Rendering the Scene

This is the final chapter of this tutorial and it will explain how to set up the scene for rendering the image you have seen at the very beginning of the tutorial.

Your car is now ready and needs an environment. We keep it simple here. Take a top view and add an Analytic rectangle. This will be the floor the car stands on, so call it Floor. You can texture that if you like and it is a good idea to make the rectangle infinitely big. To do that: select the rectangle, open Property Window at the Spec tab and check the Infinite checkbox.

Realistically rendering objects with shiny surfaces, like this car, requires the use of GI (Global Illumination). Setting up the environment for GI is easy. Create a new level under the Root level and rename that to GI Scene. In that level create a new level via the Layers -> Environments -> Sky menu. This adds a new level object to the hierarchy, called Environments. This contains a wireframe invisible mesh in the shape of a dome (or hemisphere). To carefully position the dome, make the mesh visible again by unsetting the WF Inv in the MiscTools toolbar. When done, make it WF Inv again.

Adding a sky dome to the scene

Then drop the Floor, the Environments and the Lamborghini into the GI Scene level. Select the GI Scene level and add a GI shader to it. Finally, under the Root, add a camera object. The hierarchy looks like this now:

The hierarchy after GI setup

Basically the setup is done, now it's time to do some tweaking and customizing. Let's start with the Environments level (our sky dome). Select the mesh level inside the Environments level and open its properties at the Col tab. Make sure the texture map method is set to Illumination map and select your favorite sky texture. Illumination maps add diffuse light (no hard shadows) to the scene using the colors of your texture. So if you take a blue sky, the effect is that bluish light is added to the scene; change it to a darker, orange yellowish sky with a sunset, and the effect on your render changes dramatically. It is advisable to set up some simple scenes (just a shiny sphere on a floor) and test (small 200 * 200 renders) the outcome before final rendering.

Properties for the sky dome mesh

Next, let's have a look at the GI. If you would now render  the scene, the resulting image probably will be quite dark. Note that you don't have any light sources in the scene (maybe except the standard flash light settings in the camera object). You can add light sources if you like, but it is not required to light the scene in this case.

The GI rendering results are a combination of several ingredients:
1. Brightness of the colors used in the sky dome texture;
2. Settings in the current scene camera
3. Settings in the GI_shader you applied to the scene;
4. Settings in the Post Image Effects tab;
5. Settings in the File Rendering window.

The colors in the sky dome already have been addressed here, so let's have a look at the camera. Select the camera object in the hierarchy and open its properties at the Spec tab. For the best results, when working with GI, it's advised to set the Flashlight to black. Click the grey colored icon and select a black icon in the colors window that pops up. You can also manually enter three zeroes (with spaces in between) at the input field; the result is the same:

Flashlight set to black for better GI results

The manual explains rather in depth how the GI_shader works (have a look at the Advanced Illumination Examples, specifically at the Global Illumination Components paragraph). An excerpt from the manual, about the controls of the GI_shader:

RayCount1 - The amount of GI samples at surfaces directly visible from thecamera. Usually this is the most important quality setting for indirect illumination. The higher the sampling, the lower 'Iterations' value can be used in the 'GI_blur' filter. The result is finer detail and higher realism in global illumination.
RayCount2 - The amount of GI samples at reflected surfaces. Increasing this helps to render sharp, noiseless mirror reflections of indirectly illuminated areas of the scene.
RayCount>=3 - The sampling quality for surfaces visible through double reflections, glass etc. Increasing this value helps to render sharp, noiseless images of indirectly illuminated areas of the scene which are visible through glass objects.
Contrast - Enhances local details in the global illumination. Weakly visible surface details such as low bump maps tend to disappear in strong indirect illumination. Increasing Contrast makes them more visible.
GI Bounces - The tracing depth of indirect illumination. Usually 3 bounces is enough. However, in special situations, such as when the indirect illumination comes through glass layers (windows), higher values may be necessary. Higher values also increase realism and brighten the image.
GI Reflection - Controls the brightness of indirect illumination that is visible through reflections and transparent objects

Basically it comes down to the following rule: higher ray counts produce better images (less grain), but you pay for that in terms of rendering time. You have to experiment for your own and that takes time. Try values like 10 or 15 for Raycaount1 for starters. Use small image sizes (like 300 * 200) when doing tests saves a lot of time! Also when testing, in the File Rendering window, make use of the Render and Backup Ray Trace option and Post Process option.

Real time savers, these options in the File Rendering window!

Using GI also requires you make use of the post processing system that Realsoft3D offers you. In the Select Window, click the Post Image Effects tab. Then double click on the GI_effects icon. The GI_effects basically is a container with some effects inside. You can add or remove these 'inner effects' simply via the properties of the GI_effects. To apply this 'container of GI_effects' to your scene you have to drag and drop the GI_effects icon from the Post Image Effects tab in the view window. After modifying one or more effects inside the GI_effects container, you have to drag and drop the GI_effects icon in the view window again to make your changes effective.

Double click on the GI_effects icon and you get the following window:

The GI_effects property window

The lower half of the window shows the list of effects that are ' inside the container' and there are some in the list you don't need. Select the Render particle effects and then click the Remove button. Repeat that for the Render glow material properties. For each of the effects in the container, you can change the properties as well. This is done in the Post Image Effects tab itself. There are two important effects in the container we wish to address here: GI_brightness_control and GI_blur.

ADVERTISE

As the name already suggests, GI_brightness_control gives you control over the overall image brightness. The brightness is controlled via a curve. You can access the curve by double clicking on the GI_brightness_control icon in the Post Image Effects tab. The curve shows the RGB values of the knot points on the curve. You see only the red curve, because it is exactly on top of the blue and the green one. So it is possible to change, for instance, only the red component in the image to brighter or darker. If you click and move a knot point, the underlying curve appears. To select all curves at the same time, simply drag a box around the knot point and then move it. Which curve shape is best, is again a matter of trying out. Keep the curve's minimum and maximum values between 0 and 1.

This curve produces rather dark results...

 
and this curve produces much brighter results!

The GI_blur is a time consuming parameter: higher values lead to longer render times. GI_blur blurs out the grain which is caused by low ray counts in the GI_shader. Remember that heavy blurring can cause loss of detail and also leads to longer render times. Try for instance Blur level = 7 and Iterations = 10 to start with. Again, you can decide the parameters here, testing will tell you which settings are best.

Blur Level = 7 and Iterations = 10

The last part in the setup is the File Rendering Window. As you probably know, this window has a lot of options. Here we only want to make sure that all the settings you have applied in your scene are also taken into account when rendering the image. The important part here is the Settings section. You must have selected GI Rendering in the Rendering Settings field and GI_effects in the Effect/Image field. If you forget this, the image will render with the default rendering configuration and there will be no GI applied.

Rendering Settings and Effect/Image are set for GI

This concludes our tutorial. Thanks for taking the time to read it and try it all. Share your results on the mailing list! And if we can do anything to help, just let us know.

Robert den Broeder (aka 'Spliney')
Stefan Klein (aka 'Blockbuster')

July 2006.

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