Graphics Reference
In-Depth Information
we can use a polygon offset command to increase the depth values
written to the texture.
// clear depth buffer
glClear( GL_DEPTH_BUFFER_BIT );
// disable color rendering; only write to depth buffer
glColorMask ( GL_FALSE, GL_FALSE, GL_FALSE, GL_FALSE );
// reduce shadow rendering artifact
glEnable ( GL_POLYGON_OFFSET_FILL );
glPolygonOffset( 4.0f, 100.0f );
We render the scene from the point of view of the light into a depth
texture using the following steps:
1.
Set up a MVP matrix using the eye position.
The MVP matrix setup consists of the same code as in Example 14-24,
with the exception that we create the view transformation matrix by
passing the eye position to the
esMatrixLookAt
call as follows:
// create a view−matrix transformation
esMatrixLookAt ( &view,
userData−>eyePosition[0],
userData−>eyePosition[1],
userData−>eyePosition[2],
0.0f, 0.0f, 0.0f,
0.0f, 1.0f, 0.0f );
2.
Render the scene using the shadow map created in the first
rendering pass.
Example 14-27 shows the vertex and fragment shaders that we use to
render the scene from the eye position.
Example 14-27
Rendering from the Eye Position Shaders
// vertex shader
#version 300 es
uniform mat4 u_mvpMatrix;
uniform mat4 u_mvpLightMatrix;
layout(location = 0) in vec4 a_position;
layout(location = 1) in vec4 a_color;
out vec4 v_color;
out vec4 v_shadowCoord;
void main()
