Order Independent Transparency in Max 9 - can't get it to work

Hi!

The attributes depth_sort and transparency control two different aspects of rendering.

depth_sort enables sorting draw calls based on each object’s distance from the camera. When it is enabled, the distance between each object’s position and the camera position is calculated before rendering, and the objects are then drawn from farthest to closest. This check is done per object, which means that when parts of two objects overlap, there is no single correct rendering order that will work in every case.

@transparency enables Order Independent Transparency, a technique that approximates correct rendering of semi-transparent objects regardless of draw order. It is generally more robust than depth sorting for overlapping shapes, but it requires that objects in the scene have a jit.gl.pbr attached.

That explains why things were not working in your tests:

With @depth_sort 1, transparency can still fail when objects overlap. And @transparency 1 did not work because there were no jit.gl.pbr objects attached to the gridshape objects.

Here is an example patch using @transparency 1 with jit.gl.pbr:

jit.gl.pbr applies physically based shading to objects, but if you want flat shading while still using transparency, there is a hacky but workable solution:

1. Add a dummy jit.gl.light @diffuse 0 0 0 to the patch. This overrides the default hemisphere light.

2. Set @mat_diffuse to 0 0 0 A, where A is the alpha value you want. Then control the shapes’ color using the jit.gl.pbr attribute @mat_emissive.

See your modified patch below: