GLSL 1.5& OpenGL 3.3:将颜色传递给顶点着色器似乎失败了

时间:2010-12-07 02:48:23

标签: opengl attributes colors glsl vertex-shader

将顶点属性传递给正在运行的着色器程序时出现问题。我想传递两个属性,即位置和RGBA颜色。绑定属性位置适用于该位置。但是,它不适用于颜色。因此,所有几何体最终都呈现为黑色。

这就是我的所作所为:

GLuint programHandler;

// create program
// compile & attach vertex shader
// compile & attach fragment shader

glBindAttribLocation(programHandler, 0, "InPosition");
glBindAttribLocation(programHandler, 1, "InColor");
glBindFragDataLocation(programHandler, 1, "FragColor");

glLinkProgram(programHandler);
glUseProgram(programHandler);

// initialize uniform variables

// I'm trying to get the attribute locations now.
// I expect location "0" for InPosition and location "1" for InColor.
// In fact, it gets me a "-1" for InColor. I simply cannot see the reason for that behaviour

GLint positionLocation = glGetAttribLocation(programHandler, "InPosition"); // returns 0
GLint colorLocation = glGetAttribLocation(programHandler, "InColor"); // returns -1

glEnableVertexAttribArray(positionLocation);
glEnableVertexAttribArray(colorLocation); // fails!

我的顶点着色器非常基本。我真正做的就是转换顶点并将颜色传递给片段着色器:

#version 150 core

// input
uniform mat4 ModelviewMatrix;
uniform mat4 ProjectionMatrix;
in vec3 InPosition;
in vec4 InColor;

// output
out vec4 PassColor;

void main(void) {
    // passing color through to fragment shader
    PassColor = InColor;

    // transformation
    gl_Position = ProjectionMatrix * ModelviewMatrix * vec4(InPosition, 1.0);
}

我的片段着色器应该只返回那种颜色:

#version 150 core
precision highp float;

// input
in vec4 PassColor;

// output
out vec4 FragColor;

void main(void) {
    FragColor = PassColor;
}

为什么绑定“InPosition”工作而“InColor”不工作?我知道GLSL编译器优化着色器代码,因此不能绑定未使用的变量。但是,我不明白为什么这里应该优化颜色。毕竟,我通过将它传递给片段着色器来使用它。

1 个答案:

答案 0 :(得分:1)

盲目拍摄,我认为这是错误的:

glBindFragDataLocation(programHandler, 1, "FragColor");

应该是:

glBindFragDataLocation(programHandler, 0, "FragColor");