Opacity map problems

funkdelic

Hey there,

I´ve been hitting my head on the wall for a few hours now trying to find a solution to this simple problem ( at least it seems simple )

Well, all that I wanted is to have a mask that shows only the front of my character, I have a opacity map covering the whole body but the belly, finger, toes and back details, the problem is that when I render the mask the back details are also rendering, and, well, I dont want them to show on the front render, any ideas?

Did i make myself clear?
Hope someone help me =]

Mark Dygert

1) What app.
2) How is your opacity map saved? Is it in the alpha of a TGA or a separate map?
3) How did you construct your shader?
4) Is what's on the right a render or is that your opacity map? If its a render you should probably render against a different background color because that's confusing.

You will probably need to include in your shader some type of backface culling, a Fresnel falloff or some type of camera facing calculation.

You could also try using a matte/shadow material instead of opacity, that should block visibility of the back facing visible pieces and allow the whole mesh to cast a shadow. But you have to be careful because the opaque parts will also knock out anything the character stands in front of. So for example if you rendered the character against a brick wall, you wouldn't get just the white bits, the brick wall would be missing/cut out out where ever the matte/shadow is. BUT if you rendered the background separately and composites the character it would work fine. You'll probably have to mess around with it, because this probably sounds like nonsense... but its another option to explore.

funkdelic

Thx for the reply mate!

I'm using 3dsmax, the shader is simple, just 2 maps, .png textures, one with alpha information and a default diffuse.

The img on the right is a render of the opacity map, I was showing the back details that I didnt want to show in the render.

Giometric

What you've got in the render is actually the correct behavior for what you have set up currently. What's happening now is that since the front is transparent, the back things are showing through this transparency, which is correct. If you need the front to be black but still occlude the back parts, you might set it up to where instead of rendering the opacity map, you render it with a constant shader that uses this opacity map as the color texture. Then use the RGB channels of the render (which will look like this but without the back things) instead of the alpha channel (which will have the entire character).

As a side note, I don't know what the 3dsmax equivalent would be to a constant shader, but basically use whatever shader renders just the color or texture you specify without any shading at all.