Shading Technique - Linear Depth Buffer

Overview Why using a custom Depth buffer? The default depth buffer generated by Horde3D is a non-linear depth buffer and it is relative to the "Z Far" and the "Z Near" parameter. If you need to create screen space shader like "Depth of field" and "Screen Space Ambien Occlusion", a non-linear depth buffer could cause some problems since you will need to linearize the depth buffer each frames and any changement to the Z far and the Z near could affect any shaders using the Depth Buffer. Requirements: - Basic knowledge of the Horde3D pipeline system. The shader Can be put in the ATTRIBPASS or AMBIENT context to be used with the examples pipelines in the Horde3D SDK 1.0 beta. Vertex shader: Here, you can change the max distance constant. It determine the range and the precision of the depth buffer. As you can see, there is two ways to calculate the depth of a vertex. The first one is to take the view space position of the vertex, and with this, you can take the Z value to get the depth. The second way is to create a vector from the view position to the vertex position, wich gave a slighter different result. Linear Depth - Vertex Shader // Viewer position uniform vec3 viewer; // Depth vertex color varying vec4 vVertexColor; // Black/near --> White/far // Text coord varying vec2 vTexCoords; attribute vec2 texCoords0; const float MAX_DISTANCE = 1000.0; void main( void ) { // Calculate world space position vec4 pos = calcWorldPos( gl_Vertex ); // Calculate view space position vec4 vsPos = calcViewPos( pos ); // Calculate Depth float distance = -vsPos.z / MAX_DISTANCE;//length(pos.xyz - viewer) / MAX_DISTANCE; // Colorize the vertex with the distance vVertexColor = vec4(distance); gl_Position = gl_ModelViewProjectionMatrix * pos; } Fragment shader: Linear Depth - Fragment Shader varying vec4 vVertexColor; void main( void ) { gl_FragColor = vVertexColor; } How to use it You must put the shader in EACH shaders that need to be affected by the depth buffer. Example Result To be added. Pictures To be added. To-Do List for this Article - Add an exemple - Add a picture - Add an exemple pipeline

Technique - Linear Depth Buffer [[Image:]] Creating a custom linear depth buffer Version: 1.0 Compatible with Horde3D: 1.0 beta Release date: 2008-08-10 Author(s): Mikmacer