johnLIC Posted April 22, 2016 Share Posted April 22, 2016 I'm finding a lot fo great resources to do trail effects in Houdini, but I have a question. I'm trying to do headlights and tail lights on a moving car. How would you make a trail effect that mimics a long exposure, where the trail is not present when the light source is pointing away from the camera, or occluded by the body of the car? In the attached image the cars tail lights are only visible when the car is turned away from us. Am I over-thinking this? Is there a quick solution? 1 Quote Link to comment Share on other sites More sharing options...
Juraj Posted April 24, 2016 Share Posted April 24, 2016 Hi, check this nice video with breakdown. It should not be difficult to do it. Choose points from geometry and collect them during animation. Then create flat grid based on those points. Create some attributes like age which will be used in shading. Then create UV's and you can control intensity of light in shader by ramp (along vertical and horizontal axes). I can try to create example file if you want. Juraj Quote Link to comment Share on other sites More sharing options...
johnLIC Posted May 11, 2016 Author Share Posted May 11, 2016 Thanks. This problem went away for me before I had to solve it, but someone did it in Maya by setting the motion blur shutter to 20 frames. I don't know what renderer, maybe mental ray. Quote Link to comment Share on other sites More sharing options...
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