Proper workflow for camera mapping

[simmsimaging]

I have been playing around for some time now and I am not sure I'm on the right track. The goal is to do a camera mapping of a background image onto a ground plane so that I can place objects on it and pick up reflections and cast shadows.

I have the map projections worked out (camera map per pixel map, camera map modifier on the object), but what is the right way to set up the material for my ground plane? Should I be using the projection image map in a Vray Light Mtl? This gives me a sort of 'zero' illumination so it matches the brightness of my shot, but it doesn't catch any shadows so things in contact look a little overly bright.

If I put it in the diffuse slot of a regular mat I can get shadows, but then it gets double lit, or under lit in some areas, and doesn't look right either. What is the correct or typical way to do this?

Thanks in advance.
b

[chrisjacks21]

I have used this technique a few times before too, works really well. From memory I think I used a regular vray mat with the background projected image in the diffuse slot. If you make you ground plane/object that has this material applied a matte obj (-1.0 affect alpha & shad checked), you can simply composite the 2 together in post or even render with your background environment image in place. As you say you may get 'double lighting' (didnt seem to be an issue on my project) but you could counteract this by darkening off the diffuse image if neccessary. Shadows and reflections worked nicely for me this way.



Hope this helps!

[rivoli]

you can try turning the plane into a matte object, alpha -1 and shadows and affect alpha checked, and then comp the rendered objects on a clean backplate. you should be getting reflections from the ground plane, and contact shadows from the matte, with both a plain vray mat and vray light mat.

edit:
took a bit too long to type but I was trying the vray mat and vray light mat thing.

[simmsimaging]

Thanks Chris and Rivoli - I will give it another try using it as a matte object. I was having trouble figuring out how to use that and still get the shadows, but I have that sorted out now too.

Thanks again for the help - and that sample looks great Chris!

b

[simmsimaging]

So far this is working out well now, but one thing I can't get is the viewport to display the camera map per pixel image when using VrayPhysical Cameras for the projection. They render okay, but you can't see them. Is that just me or is this a known issue?

Easy enough to add a Max camera just for the camera-mapping, but it took me a while to figure out what was actually wrong

b

[ruffstuff]

Camera map per pixel doesn't show in the viewport, There was talk at Autodesk of making it work with viewport pixel shaders, but it never happened. I think you can subvide the mesh a bit and add a camera map modifier to the object. Turning on show map in viewport for the texture would then show it in the viewport also.

Fred

[tryharder]

... nice tip

[simmsimaging]

Thanks Fred - I didn't realize it was the camera map modifier making it work in the viewport, but that still doesn't seem to work with VrayPhysical camera.

b