Caustics in H11???

[crash0283]

Hey Guys

I'm rendering some glasses and trying to use caustics in h11. I was wondering how do you render caustic using the caustic light? The old way was to set up two mantra nodes, one being the photon map generator and the other your pbr node, but since lighting has changed in h11 how would you go about setting this up? I have a spot light, a point light, and a caustics light. I want the point light to light the scene and the spot light to be used to generate photons. I know that under the light mask in the caustics light I have to specify to use the spot light, but how do I render the scene using the light from the point light and the photons from the spot light? Thanks.

Chris

[Macha]

Like this?

caustic.hip

[Macha]

Ho, I see your confusion.

The lightmask doesn't appear to work properly.

You can work around by disdabling the spotlight's diffuse and setting its strength very very low while at the same time increasing the caustic light. That way you only generate caustic light by having no or very little contribution to the rest of the illumination.

Unless I missed something obvious.

[LaidlawFX]

under the help for the indirect light is a .otl for caustics, TubeCaustic.otl It's very helpful.

[crash0283]

Thanks guys!!! The tubecaustic.otl was very helpful...but, I had one other question. Is there a shader such as the "use background" shader in Maya in Houdini? Or if not, is there a way to achieve the same effect? Thanks.

Chris

[LaidlawFX]

Thanks guys!!! The tubecaustic.otl was very helpful...but, I had one other question. Is there a shader such as the "use background" shader in Maya in Houdini? Or if not, is there a way to achieve the same effect? Thanks.

Chris

I forget what the closest direct translation is, but you can use the phantom check box on the geometry node to get around a couple of the problems that you would use that in.

[crash0283]

Hey Ben

Thanks for the quick response...the only problem is that I want all the shadows, caustics, reflections, etc. to show up...only without the "floor" surface. When I use the "phantom" option, this doesn't work. Any other suggestions? Thanks again.

Chris

[LaidlawFX]

You can hack a shadow map, and add reflection to it(and anything else you want). You just have to take those reflections and convert them through a luminance node to B&W and add it to your shadow map then clamp it from 1 to 0.

I remember the last time I did this PBR wasn't my biggest friend, micro works with the shadow matte node the best. I know other people have asked this question before.

[Gimmerz]

You can hack a shadow map, and add reflection to it(and anything else you want). You just have to take those reflections and convert them through a luminance node to B&W and add it to your shadow map then clamp it from 1 to 0.

I remember the last time I did this PBR wasn't my biggest friend, micro works with the shadow matte node the best. I know other people have asked this question before.

Hi LaidLawFX, i wonder if you could explain your process a little more. Im trying to produce a separate pass for my caustics but I cant get it with out the ground rendering. I had a feeling you could do it with the shadow matte but I cant figure out your hack. Any example files would be a great help.

Thanks

G

[LaidlawFX]

Hi LaidLawFX, i wonder if you could explain your process a little more. Im trying to produce a separate pass for my caustics but I cant get it with out the ground rendering. I had a feeling you could do it with the shadow matte but I cant figure out your hack. Any example files would be a great help.

Thanks

G

For a simple solution, If you just want the caustics of the ground in say the tube caustic example why don't you just create a white(green) matte of the tube and the ground(red) and use the pre-built render pass(or another render node and render take) to export them?

I tried to put the ground as a phantom object, but that seems to not be able to work with the tube caustic example. I think for the same reason that there are no caustic on the tube, since the tube is the photon target that is creating the photons, so the only "caustics" you see on the tube are just reflections. So I turned on the all_reflect image plane after exchanging the old school shaders for the mantrasurface shader to extract that and that got me my reflection. direct_reflect didn't work, so I think you really just need indirect_reflect.

Caustic.hip

As for some shader hackery like I said in the custom matte, you could just dive inside the mantrasurface find the indirect_reflect parameter, and make a matte for the tube, but I think if you want an example of that type I need another example file, or a simple concept to proof outside the tube_caustic example. My brain runs a little dry at the the end of the day.

[Gimmerz]

For a simple solution, If you just want the caustics of the ground in say the tube caustic example why don't you just create a white(green) matte of the tube and the ground(red) and use the pre-built render pass(or another render node and render take) to export them?

I tried to put the ground as a phantom object, but that seems to not be able to work with the tube caustic example. I think for the same reason that there are no caustic on the tube, since the tube is the photon target that is creating the photons, so the only "caustics" you see on the tube are just reflections. So I turned on the all_reflect image plane after exchanging the old school shaders for the mantrasurface shader to extract that and that got me my reflection. direct_reflect didn't work, so I think you really just need indirect_reflect.

Caustic.hip

As for some shader hackery like I said in the custom matte, you could just dive inside the mantrasurface find the indirect_reflect parameter, and make a matte for the tube, but I think if you want an example of that type I need another example file, or a simple concept to proof outside the tube_caustic example. My brain runs a little dry at the the end of the day.

Hi, thanks for having a look at this, I had seen the tube example and at first glance thought that the object mattes (obj_matte_pointlight_photons_direct_diffuse) created in the image planes were going to give me the result I was looking for. The problem however is still there, even in the mattes you don't get just light/caustics, there is still geometry there, ground plane and tube. Id like to get the caustics completely free of the objects as you would in a shadows pass. Also, when saving out the obj_matte... to a .tif I expected to actually get what I saw in mplay, however when i open th e .tif its the full image, colour and all, no longer a matte of any sort. How do you save those mattes... as mattes? Im going to have to look at this further thanks for your help, G

[LaidlawFX]

Hi, thanks for having a look at this, I had seen the tube example and at first glance thought that the object mattes (obj_matte_pointlight_photons_direct_diffuse) created in the image planes were going to give me the result I was looking for. The problem however is still there, even in the mattes you don't get just light/caustics, there is still geometry there, ground plane and tube. Id like to get the caustics completely free of the objects as you would in a shadows pass. Also, when saving out the obj_matte... to a .tif I expected to actually get what I saw in mplay, however when i open th e .tif its the full image, colour and all, no longer a matte of any sort. How do you save those mattes... as mattes? Im going to have to look at this further thanks for your help, G

I'm guessing I haven't seen the pass before that you are looking for...

Do you want a solid white matte of the caustics pattern? You can just create that in comp by color correcting it or in, the shader by fit ranging it to an appropriate level. I would do it comp though since you have the whole range.

The pass you get from a shadow matte is still defined by the geometry it doesn't disappear, the shading from the shadows create shape that is the only difference between it and a paint/color layer. So a pure diffuse layer with out color, is a really a type of shadow pass, as is an occlusion pass. So do you just want an on and off switch like an alpha for your caustic pattern?

Only .exr and .rat can receive mutliple layers, which is why you can't see it in a tiff. For the matte I created it isn't separate layers you just pull the red, green, or blue values as a matte, on a simple image it is easier than creating a matte for each object as a separate layer, or all from one layer with float numbers like a shaderID, or an objectID for the boundary edges between shapes gets crunched.

I would say bust open nuke and you'll be able to comp out what you want.

[Gimmerz]

I'm guessing I haven't seen the pass before that you are looking for...

Do you want a solid white matte of the caustics pattern? You can just create that in comp by color correcting it or in, the shader by fit ranging it to an appropriate level. I would do it comp though since you have the whole range.

The pass you get from a shadow matte is still defined by the geometry it doesn't disappear, the shading from the shadows create shape that is the only difference between it and a paint/color layer. So a pure diffuse layer with out color, is a really a type of shadow pass, as is an occlusion pass. So do you just want an on and off switch like an alpha for your caustic pattern?

Only .exr and .rat can receive mutliple layers, which is why you can't see it in a tiff. For the matte I created it isn't separate layers you just pull the red, green, or blue values as a matte, on a simple image it is easier than creating a matte for each object as a separate layer, or all from one layer with float numbers like a shaderID, or an objectID for the boundary edges between shapes gets crunched.

I would say bust open nuke and you'll be able to comp out what you want.

Hi, basically what I need is to be able to get the caustic pass to have a transparent layer, as in creating a shadow matte (I know that the shadow pass is defined by the geo but what im saying is when the shadow matte is created it has that transparency for the rest of the image) thus you get the shadow and the rest of the image is transparent. Im going to be casting coloured caustics so I wanted the layer/matte to have the colour info where the caustics are cast and to have the transparency around the rest of the layer. Any thoughts? I will bear the .exr and .rat files in mind next time so thanks for that pointer : )

[LaidlawFX]

Hi, basically what I need is to be able to get the caustic pass to have a transparent layer, as in creating a shadow matte (I know that the shadow pass is defined by the geo but what im saying is when the shadow matte is created it has that transparency for the rest of the image) thus you get the shadow and the rest of the image is transparent. Im going to be casting coloured caustics so I wanted the layer/matte to have the colour info where the caustics are cast and to have the transparency around the rest of the layer. Any thoughts? I will bear the .exr and .rat files in mind next time so thanks for that pointer : )

You can't get an alpha for your caustic. Just do it in comp with that pass, it is the same as a possible shader trick as described already. Those image layers do not have separate alphas.