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TOPIC: Procedural Carpaint

Sihina_lahiru

Senior Member

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Posts: 145

Date: Dec 17, 2009

Procedural Carpaint	Permalink

By the time Speed Racer is smashing this summer´s box offices I thought it might be nice to finish a tutorial I started about a year ago It´s a small people tutorial and the renderings are far from photoreal but it gives you and idea of what can be done in post production… The images above are done from ONE SINGLE 3D rendering session providing all the passes we need to change pretty much everything in post without re-rendering in 3D which can eat production/render time when the customer is a bit moody with his decisions... The layers I rendered as well as the After Effects Project file are all featured in this tutorial and can be downloaded here: Project and Render Files I wouldn´t go any deeper into After Effects or provide the Max file since this an intermediate compositing tutorial. You can read about Ambient Occlusion, Falloffs and Blend Options in your Max/After Effects Help yourself No basics covers, I´m sorry. So let´s go! Step 1: This tutorial works with simple tricks! Nesting Compositions into each other and setting Mattes (called knock out layers) with alpha and falloff passes we rendered.We start with a new Composition and drag the Ambient Occlusion rendering into it. An additional added Brightness&Contrast can be used to eventually adjust the layer to have more or less AO going on. Step 2: Our base coat layer, believe it or not, consists of two color solids! I add Hue/Saturation to both of them and adjust the colors to my desire by shifting the color, saturation and lightness. Having 2 different color solids creates the chamelion look later ;). I use the Carpaint Falloff rendering to blend them nicely into each other. An additional Brightness &Contrast can be used to modify the hardness of the Falloff. Step 3: Since the color Solids are still full screen we need to use a matte to cut out the car body. Drag the whole Base Color composition into a new composition and use the Carpaint Mask rendering as Luma Matte. The Carpaint Mask is actually a B/W rendering with a white self-illuminated material applied to the car body. The rest of the scene has a black self-illuminated material applied. The result is a nice mask. Step 4: Time for the nice reflecting clear coat. Actually it is rendered as a full reflecting mirror. Drag the Carpaint Mirror rendering into a new composition and use the Carpaint Mask rendering again as Luma Matte. We will use the Carpaint Falloff rendering later to blend it with the rest of the layers. An additional Brightness &Contrast can be used to modify the Falloff then. Step 5: Specular metallic layer. Drag the Specular render layer (a simple noise map on the car body) into a new composition and use the Specular Falloff to knock out a nice alpha that will blend the metallic paint and will reveal the base coat underneath to gain the nice metallic specular paint effect. U can use a Brightness&Contrast and/or a Hue/Saturation to adjust or color the specular layer. I tinted it a little red e.g. Step 6: Details. I rendered the non carpaint details like lamps and tires into one single layer. That can be split up into more of cause. Drag the Detail rendering into a new composition and use the Detail mask to knock out the alpha. This masked was generated the same way the Carpaint Mask was done. Black and white Self-illuminated materials applied to objects. White to what you wanna keep, black what you wanna knock out. Step 7: Glass. I rendered the glass as a full reflective mirror just like the clear coat and a fresnel falloff for the alpha so it behaves like real glass. Drag the Glass Mirror into a new composition and use the Glass Falloff as mask. I wanted to make the wind shield less transparent because the car doesn´t have any interior. I added a black solid color that covers only the wind shield underneath the glass and used the glass mirror as alpha mask to knock out the windows only. Step 8: A simple Ground Shadow layer I rendered using a Matte/Shadow material on the ground to provide an alpha channel to the shadow. I set the whole car to “Cast Shadow” but to “Invisible to Camera” and “Invisible to Reflections” at the same time modifying the object properties (right click on a selected object). So the car casts a nice shadow with out being visible at all. Just drag that layer into a new composition. No masking this time. Step 9: This is where the magic happens! All the above was just preparation Now we will put it all together. We work from back to front. Start with a new composition and set the background to a color /gradient u like best. Drag the ground shadow composition into the new composition. Drag the Detail composition in next. The details have an alpha so they should fit well. Time for the base color composition. Add the specle comp on top. The falloff in this comp will reveal it where light hits. I added the Ambient Occlusion composition next just because it looked cool here NOTE that I set the Layer Mode to Multiply to have a nice overlay/add look going on. Add the clear coat comp on top. NOTE that I used the carpaint falloff as luma matte. Now add the glass composition. The FX Adjustment Layer is optional. In my case I added glow and lense flare FX. Remember that you can get back into the sub-compositions at any time to make adjustments. The Brightness&Contrast adjusts the hardness of the falloffs, the Hue/Saturation adjusts the color, lightness and saturation of the solid color layers etc. By changing the opacity of certain layers or their layer blend mode (e.g “Overlay” or “Multiply”) you can adjust the amount of specular/metallic or heaviness of the clear coat e.g. Playing with all these possibilities I got kinda cool results in NO time: Additional Note: This tutorial is not necessarily an After Effects tutorial. If you understand the meaning of nesting and blending layers you can tranfer the steps to almost any compositing. If you render a normal pass and UW pass you can even decorate the car with decals and dirt etc. in post! Since you can´t import 3D data into After Effects properly I skipped this part here. Entire relighting can be done with the 3D geometry as FBX or OBJ and the normal pass too I didn’t render Velocity or Z-Buffer because the image is clearly a still image and the most far point in it is aprox. 5 meters in the back. Since I wanted the whole car to be sharp I didn´t need any Z information. Talking about Falloffs briefly: Below you can see two of the Falloffs I used. Again this is not a shading tutorial so I´ll cut that short here J For the reflection and Color mix of the Base Coat colors I used a fresnel falloff in camera Z-Direction with a bit sharper curve and overriden IOR setings. For the Specle/Metallic blend falloff I used a Perpendicular/Parallel falloff. The glass falloff is fresnel again to cut away reflection as the camera turns away from the object surface. Lots of other websites and portals released articles and interviews about Speed Racer lately. I would like to point out one in particular: VFX Guide Article: How to Paint a Digital Car And again I invite you to go crazy on the settings J This time I used an image as the first base color (instead of the darker red) and shifted the Hue/Saturation effects to a golden yellow…Note that the this was done without UVW coordinates and normal pass renderings. This is straight faking But certainly it does the trick at least for a still. As the great Brandon Davis says: Physically correct is not necessarily aesthetically correct! And YEEES I admit sometimes I like the cheeeeesy glow especially for show cars! Looks more glamorous and hides minor flaws in the geometry… __________________

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