Vaios’ Blog

Today I implemented depth parallax on a quad with two textures. The algorithm creates the illusion that we have two surfaces instead of one. It’s really cool! Check out the screenshots below. The first one shows the initial multi-textured quad. The blue texture is the outer layer and you can see the inner texture through it.

Now this is the same quad after we rotate the view. The depth parallax algorithm creates the illusion of depth.

The code for doing this is pretty simple; we use a simple pixel shader and an even simpler vertex shader. We don’t even have to enable blending or even multi-texturing! We just pass the textures to the pixel shader and let it compute the final color for us.

In this project we are going to implement the algorithm presented at “Rendering Semitransparent Layered Media” [Oat2006]. Modern graphics hardware provides the capability to apply many texture layers onto a single surface. However, simply alpha blending many textures onto a surface does not give the appearance of surface depth that one would expect from semitransparent surface layers. Normal mapping, transparency masking, offset mapping and image filtering are combined in this method to produce realistic looking layered surfaces.

The method presented in the paper achieves the look of a volumetric material by exploiting several perceptual cues, based on depth and illumination, while combining multiple material layers on the surface of an otherwise non-volumetric, multi-textured surface such as the human heart shown in the first page. Multiple implementation strategies are suggested that allow for different trade-offs to be made between visual quality and runtime performance and we are going to investigate which one works best for our implementation.

You can download the design doc here