Graphics Reference
In-Depth Information
Example 8-8
Displacement Mapping Vertex Shader
(continued)
layout(location = 1) in vec3 a_normal; // input normal value
layout(location = 2) in vec2 a_texcoord; // input texcoord value
layout(location = 3) in vec4 a_color; // input color
// vertex shader output, input to the fragment shader
out vec4 v_color;
void main ( )
{
v_color = a_color;
float displacement = texture ( displacementMap,
a_texcoord ).a;
vec4 displaced_position = a_position +
vec4 ( a_normal * displacement, 0.0 );
gl_Position = u_mvpMatrix * displaced_position;
}
We hope that the examples discussed so far have provided a good
understanding of vertex shaders, including how to write them and how to
use them for a wide-ranging array of effects.
Vertex Shader
We now discuss a vertex shader that implements the OpenGL ES 1.1 fixed-
function vertex pipeline without vertex skinning. This is also meant to be
an interesting exercise in figuring out how big a vertex shader can be and
still run across all OpenGL ES 3.0 implementations.
This vertex shader implements the following fixed functions of the
OpenGL ES 1.1 vertex pipeline:
• Transform the normal and position to eye space, if required (typically
required for lighting). Rescale or normalization of normal is also
performed.
• Compute the OpenGL ES 1.1 vertex lighting equation for up to eight
directional lights, point lights, or spotlights with two-sided lighting
and color material per vertex.
• Transform the texture coordinates for up to two texture coordinates
per vertex.
