loudsubs Posted August 12, 2011 Share Posted August 12, 2011 Hi, I'm getting a weird highlight in certain frames of my render. Im using a chrome-like shader and lighting it with an env light with an HDRI isixpack envmap. I'm stuck on why I keep getting these really blown out highlight areas. The RGB values for the brightest point in some of the highlights is 10. I get the same result with PBR and raytrace rendering. Can anyone tell me whats causing these sharp highlights? Thanks. Quote Link to comment Share on other sites More sharing options...
LaidlawFX Posted August 12, 2011 Share Posted August 12, 2011 Hi, I'm getting a weird highlight in certain frames of my render. Im using a chrome-like shader and lighting it with an env light with an HDRI isixpack envmap. I'm stuck on why I keep getting these really blown out highlight areas. The RGB values for the brightest point in some of the highlights is 10. I get the same result with PBR and raytrace rendering. Can anyone tell me whats causing these sharp highlights? Thanks. I usually find this to be the intensity of the hdr map. You may need to clamp the maps whites to the 2 to 4 range. Quote Link to comment Share on other sites More sharing options...
petz Posted August 12, 2011 Share Posted August 12, 2011 that´s the reason why mantra pbr really stresses the need for an appropriate tone-mapper in mplay! petz Quote Link to comment Share on other sites More sharing options...
hkspowers Posted August 12, 2011 Share Posted August 12, 2011 Hi, I'm getting a weird highlight in certain frames of my render. Im using a chrome-like shader and lighting it with an env light with an HDRI isixpack envmap. I'm stuck on why I keep getting these really blown out highlight areas. The RGB values for the brightest point in some of the highlights is 10. I get the same result with PBR and raytrace rendering. Can anyone tell me whats causing these sharp highlights? Thanks. This looks like a known problem with Mantra in Houdini 10. Peter Quint talks about the problem in this video. Look at the 4:15 mark. Lighting in H11 Quote Link to comment Share on other sites More sharing options...
loudsubs Posted August 12, 2011 Author Share Posted August 12, 2011 Hi, thanks for the replies guys. I had a closer look at my rat envmap and it appears to have no values above one, so I guess I made a mistake somewhere along the line when producing my envmap, but thats another issue. I checked the values in nuke and mplay, and none of the RGB values are above 1, so I guess its not an HDR issue since my envmap is not actually HDR. I also had a look at the Peter Quint video and that does seem similar to my problem, but there are no edge falloff options in the env light. I also did try putting the color limit param in my mantra node to 1. That gets the best results so far, by minimizing the number of bright white pixels, but there are still some present. These images below are with all the lights in the scene switched off (including the envlight), one with the displacment shader enabled, one without. And Im still getting this highlight. Seems I shouldnt be able to see anything with all the lights off. Any ideas? Quote Link to comment Share on other sites More sharing options...
hkspowers Posted August 12, 2011 Share Posted August 12, 2011 Hi, thanks for the replies guys. I had a closer look at my rat envmap and it appears to have no values above one, so I guess I made a mistake somewhere along the line when producing my envmap, but thats another issue. I checked the values in nuke and mplay, and none of the RGB values are above 1, so I guess its not an HDR issue since my envmap is not actually HDR. I also had a look at the Peter Quint video and that does seem similar to my problem, but there are no edge falloff options in the env light. I also did try putting the color limit param in my mantra node to 1. That gets the best results so far, by minimizing the number of bright white pixels, but there are still some present. These images below are with all the lights in the scene switched off (including the envlight), one with the displacment shader enabled, one without. And Im still getting this highlight. Seems I shouldnt be able to see anything with all the lights off. Any ideas? Just a shot in the dark but do you have an environment map on the material? Quote Link to comment Share on other sites More sharing options...
loudsubs Posted August 12, 2011 Author Share Posted August 12, 2011 Just a shot in the dark but do you have an environment map on the material? No env map on the material, but I am using a displacement map, and a specular map to hold down the reflections on the rust areas Quote Link to comment Share on other sites More sharing options...
LaidlawFX Posted August 12, 2011 Share Posted August 12, 2011 These images below are with all the lights in the scene switched off (including the envlight), one with the displacment shader enabled, one without. And Im still getting this highlight. Seems I shouldnt be able to see anything with all the lights off. Any ideas? If the lights are truely off then it can not be a light related problem. For an double check copy all your lights and then delete them from your scene, and test render then. If it's still there than you got other issues. If it does work then check your forced objects, your takes, and your displayvs render flags to make sure yo are not doing something by accident. If a scene has color in it with out light, it's usually and emission or constant color... probably not the case. If it is isolated to just the disp and the shader, drop that element into a clean scene by itself, and if it is still happening send in a bug report. Additionally if you're using the mantra surface shader make sure conserve energy is on, this will do a limit on the bbsdf so it doesn't go above 1. Which if lights are contributing may be a likely culprit. Quote Link to comment Share on other sites More sharing options...
loudsubs Posted August 12, 2011 Author Share Posted August 12, 2011 If the lights are truely off then it can not be a light related problem. For an double check copy all your lights and then delete them from your scene, and test render then. If it's still there than you got other issues. If it does work then check your forced objects, your takes, and your displayvs render flags to make sure yo are not doing something by accident. If a scene has color in it with out light, it's usually and emission or constant color... probably not the case. If it is isolated to just the disp and the shader, drop that element into a clean scene by itself, and if it is still happening send in a bug report. Additionally if you're using the mantra surface shader make sure conserve energy is on, this will do a limit on the bbsdf so it doesn't go above 1. Which if lights are contributing may be a likely culprit. I think I have resolved the problem. It was the simplest solution, and I should have tried in the very beginning. I deleted all the lights, and started relighting the scene from scratch -- the issue seems to be gone. So I'm not really sure if this was a bug or what was causing it, but I'm glad to be rid of the highlights. Thanks for the advice guys. And Ben, your lighting guide has been absolute gold, thanks for sharing it. Quote Link to comment Share on other sites More sharing options...
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