[英]GLSL 1.5 & OpenGL 3.3: Passing color to vertex shader seems to fail
I have a problem when passing vertex attributes to the running shader program. 将顶点属性传递给正在运行的着色器程序时出现问题。 I'd like to pass two attributes, the position and a RGBA-color.
我想传递两个属性,即位置和RGBA颜色。 Binding the attribute location works for the position.
绑定属性位置适用于该位置。 However, it does not work for the color.
但是,它不适用于颜色。 Therefore, all the geometry is eventually rendered black.
因此,所有几何体最终都呈现为黑色。
This is what I do: 这就是我做的:
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!
My vertex shader is very basic. 我的顶点着色器非常基本。 All I really do is transforming vertices and passing the color to the fragment shader:
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);
}
My fragment shader should simply return that color: 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;
}
Why does binding "InPosition" work and "InColor" does not? 为什么绑定“InPosition”工作和“InColor”不工作? I am aware that the GLSL compiler optimizes the shader code, so that unused variables cannot be bound.
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。 But, I don't see why the color should be optimized out here.
但是,我不明白为什么这里应该优化颜色。 After all, I use it by passing it to the fragment shader.
毕竟,我通过将它传递给片段着色器来使用它。
A blind shot, i believe this is wrong: 盲目的,我相信这是错误的:
glBindFragDataLocation(programHandler, 1, "FragColor");
It should be: 它应该是:
glBindFragDataLocation(programHandler, 0, "FragColor");
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