Ambient Occulusion

Ambient Occlusion is a method for simulating global illumination, while keeping a respectable ratio between results and computing times.It is a global method, meaning the illumination at each point is a function of other geometry in the scene.

Ambient occlusion is most often calculated by casting rays in every direction from the surface. Rays which reach the background or “sky” increase the brightness of the surface, whereas a ray which hits any other object contributes no illumination. As a result, points surrounded by a large amount of geometry are rendered dark, whereas points with little geometry on the visible hemisphere appear light.

Ambient Occulusions are cool cause they add depth and 3d look to the rendered image. We render ambient occulusion pass to give 3d look to objects . Many people just render their models by applying ambient/reflective occulusion as a shader. But this way they loose the previous material. But i am going to show you a quick and easy way to render ambient occulusion pass.

Rendering Ambient Occulusion In 3dsmax

Using Material Override.

Step 1

Open a new scene in 3dsmax and create a plane on the grid (exact cordinates doesn’t matter). Assign any material to it.

Step 2

Now bring some basic primitives on the plane. In this case i am using my own sniper model.

Step 3

Now apply different materials on these basic primitives. In my case i applied different materials on different parts of my sniper model. See my material editor…

Step 4

Now lets do a quick render of the whole scene.

Step 5

Now we are going to render ambient occulusion for the whole scene. So to do this we go to render settings or, press f10 to bring render scene dialogbox. In the assign renderer we select mental ray. Now close the dialogbox . Go back to material editor select any material. Go to material self illumination property turn it on and select ambient/reflective occulusion from the new material map browser and do remember to rename the material, In my case i renamed it into ambient occulusion. See my material editor…

Here we are assigining ambient/reflective occulusion to self illumination property and not to the mentalray shader ,diffuse ,or any other property because we want our scene to evenly lit from all directions.

Step 6

Now go to render settings dialog box and go to processing tab and check the material override and click on that, Now under the material map browser go to the material editor and select the ambient occulusion material. See in image below…

Step 7

Now press M and bring back material editor , Select the ambient occulusion material which we created earlier, Now go to the self illumination map property and under max distance type 4 and in samples type 64 to reduce the noise in the render.You can increase the samples value but it increases your render time too.

Step 8

Now take a render of the whole scene and you are done . You have rendered an ambient occulusion pass without lossing your previous materials. {Now if you want to bring the orignal material back just uncheck the material override checkbox and voila! you are done}. Now you can take this pass and composite it in any compositing programe. See final occulusion pass..

Related posts:

1. Wireframe Render in Maya