我的镶嵌着色器为两个顶点生成贝塞尔曲线。顶点由两个坐标 x 和 y (vec2) 组成。现在每个顶点都有颜色。我的问题:如何在生成的曲线上插入每个顶点的颜色?现在片段着色器设置一个默认颜色值(红色)。但我希望他得到插值的颜色。
例如:
vertex 1 [vec2(0.0, 0.0), vec4(1.0, 0.0, 0.0, 1.0)] // red
vertex 2 [vec2(1.0, 1.0), vec4(0.0, 1.0, 0.0, 1.0)] // blue
所以应该有一个从红色到蓝色的渐变。我怎么能用镶嵌着色器做到这一点?
顶点着色器:
#version 400
layout (location = 0 ) in vec2 in_position;
layout (location = 1 ) in vec4 in_color;
void main()
{
gl_Position = vec4(in_position, 0.0, 1.0);
}
镶嵌控制着色器:
#version 400
layout( vertices = 2 ) out;
uniform int NumSegments;
uniform int NumStrips;
void main()
{
gl_out[gl_InvocationID].gl_Position = gl_in[gl_InvocationID].gl_Position;
gl_TessLevelOuter[0] = float(NumSegments);
gl_TessLevelOuter[1] = float(NumStrips);
}
镶嵌评估着色器:
#version 400
layout( isolines ) in;
uniform mat4 Projection;
uniform mat4 Modelview;
void main()
{
float u = gl_TessCoord.x;
vec3 p0 = gl_in[0].gl_Position.xyz;
vec3 p1 = vec3(0.5, gl_in[0].gl_Position.y, 0.0);
vec3 p2 = vec3(0.5, gl_in[1].gl_Position.y, 0.0);
vec3 p3 = gl_in[1].gl_Position.xyz;
float u1 = (1.0 - u);
float u2 = u * u;
// Bernstein polynomials
float b3 = u2 * u;
float b2 = 3.0 * u2 * u1;
float b1 = 3.0 * u * u1 * u1;
float b0 = u1 * u1 * u1;
// Cubic Bezier interpolation
vec3 p = p0 * b0 + p1 * b1 + p2 * b2 + p3 * b3;
gl_Position = Projection * Modelview * vec4(p, 1.0);
}
片段着色器:
#version 400
layout ( location = 0 ) out vec4 FragColor;
void main()
{
FragColor = vec4(1.0, 0.0, 0.0, 1.0);
}