From the course: 3ds Max: Rendering with Arnold

Mapping opacity - 3ds Max Tutorial

From the course: 3ds Max: Rendering with Arnold

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Mapping opacity

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- [Instructor] Mapping opacity, or visibility of a material, is an easy matter in Arnold, using the opacity map input of the Arnold standard surface. We could use an Arnold image node for that purpose, but I prefer to use the OSL bitmap lookup, because it's got a gamma control built into it, and that can be helpful in cases where we want to remove matte fringe or halos around an opacity map. I've got the material editor open and Activeshade running. I've got a material assigned onto the leaves of this plant, and it's an Arnold standard surface. We can go down near the bottom of that node using the middle mouse button, and we'll find the opacity input. Let's connect something there. Click on that input and drag out, release the mouse, and from the pop up menu choose OSL, bitmap lookup, and in the further pop up menu, choose col, or color RGB, and now we're connected to the color output. And we do get the default test image, we double-click on the bitmap lookup node, we've got the file name set to UVgrid.png. Let's rename this while we're here, we'll call it opacity map. I've got a file already prepared. Let's go into the file name, click the browse button, and in the current projects scene assets images, I've got a sub folder plants, inside there, house plant 05, you want to select house plant 05 leaf alpha.tga. Click open and now we see we have transparency. Pretty easy, let's get in really close on the edges of the leaves here in the perspective view. Control alt and middle mouse button. Get in very very close, against something that has a lighter background, such as a planter, and if you look closely you may see a little bit of a halo there. It's just a little bit darker there on the edge than I want it to be. And I use the OSL bitmap lookup node because it has a manual gamma control built into it. Let's go over there to the opacity map parameters, disable auto gamma, and if we play with this gamma amount, we may be able to get rid of some of the halos there. I'll bring that up, and as I do it seems to remove some of those darker pixels. Okay we can play around with specific values if we set this to .1, we'll see we're getting a large fringe. With a default of 1, we're getting a bit of a halo there, if we bring it up to a value of 5, we've pretty much removed that issue. All right very cool. So we can go back to a wider shot, that's how to map the opacity of an Arnold standard surface using an OSL bitmap lookup node.

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