无法在OpenGL着色器中设置统一值 [英] Can't set uniform value in OpenGL shader

问题描述

我目前正在学习OpenGL编程，我已经取得了一些进展，但我现在已经陷入困境了。

I am currently learning OpenGL programming, and I have made some good progress, but I seem to be stuck now.

目前，我想获得简单的着色器上班。更具体地说，我想设置着色器的统一值。着色器编译成功，如果我消除了统一值，它可以正常工作。这里是（顶点）着色器代码：

Currently, I am trying to get simple shaders to work. To be more specific, I am trying to set a uniform value of the shader. The shaders compile successfully, and work correctly if I eliminate the uniform value. Here is the (vertex) shader code:

#version 440 core

layout(location = 0) in vec3 vertex;

uniform mat4 mvp;

void main()
{
    gl_Position = mvp * vec4(vertex, 1);
}

我用来设置值的代码（ glGetUniformLocation 按预期返回0）：

And the code I use to set the value (glGetUniformLocation returns 0 as expected):

mvp = glm::mat4(
    glm::vec4(3.0f, 0.0f, 0.0f, 0.0f),
    glm::vec4(0.0f, 1.0f, 0.0f, 0.0f),
    glm::vec4(0.0f, 0.0f, 1.0f, 0.0f),
    glm::vec4(0.0f, 0.0f, 0.0f, 2.0f)
);

GLuint matrix = glGetUniformLocation(program, "mvp");
glUniformMatrix4fv(matrix, 1, GL_FALSE, glm::value_ptr(mvp));

问题是它似乎根本没有设置值。如果我使用 glGetUniformfv 查询统一的值，它返回默认值（而不是我刚才设置的值），几何不会显示出来只是一个后果，这不是这里的问题。）

The problem is that it doesn't seem to set the value at all. If I query the uniform's value using glGetUniformfv, it returns the default value (not the one I just set), and the geometry doesn't show up at all (but that is just a consequence, that's not the problem here).

如果我在着色器中硬编码统一的值，应用程序正确显示几何，当要求的值再次使用 glGetUniformfv ），它返回正确的值。 vec3顶点中的

If I hardcode the uniform's value in the shader, the application displays the geometry correctly, and when asked for the value (again, using glGetUniformfv), it returns the correct value.

#version 440 core

layout(location = 0) in vec3 vertex;

uniform mat4 mvp = mat4(
    vec4(1.0f, 0.0f, 0.0f, 0.0f),
    vec4(0.0f, 1.0f, 0.0f, 0.0f),
    vec4(0.0f, 0.0f, 1.0f, 0.0f),
    vec4(0.0f, 0.0f, 0.0f, 2.0f)
);

void main()
{
    gl_Position = mvp * vec4(vertex, 1);
}

任何想法为什么会发生？我使用的是OpenGL 4.4，但我尝试了很多不同的版本，结果相同。

Any idea why does this happen? I am using OpenGL 4.4, but I have tried many different versions with the same result.

感谢您的时间和精力，

Levente

推荐答案

在设置制服之前调用glUseProgram？完整的工作列表可以在很多在线示例中找到，包括我在某个时候写的内容（ https：// github.com/prabindh/sgxperf/blob/master/sgxperf_gles20_vg.cpp ），显示序列为：

Are you calling glUseProgram before setting the uniforms ? A full working listing can be found in many examples online, including what I had written sometime back (https://github.com/prabindh/sgxperf/blob/master/sgxperf_gles20_vg.cpp) that shows the sequence to be:

glCreateProgram（）;

glCreateProgram();

glAttachShader（）

glAttachShader()

glLinkProgram

glLinkProgram

glUseProgram（）

glUseProgram()

glGetUniformLocation（）

glGetUniformLocation()

glUniformMatrix4fv

glUniformMatrix4fv

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