c++ - 让纹理在 OpenGL 3.2 中工作

Question

我已经盯着这段代码看了一段时间，但没有运气。我正在努力将 librocket 集成到我自己的项目中(库对问题来说并不那么重要)，其中一部分需要编写渲染器类。我一直在尝试这样做，但无法显示纹理。顶点颜色和位置工作正常。

我正在使用 OpenGL3.2。

我临时修改了代码以尝试绘制单个四边形。唯一使用的参数是 texture 参数，它只是一个转换为另一种类型的 GLuint。

很有可能我遗漏了一些愚蠢的东西，但我看不到它。希望另一双眼睛会有所帮助。欢迎索取更多代码/信息。

// Called by Rocket when it wants to render geometry that it does not wish to optimise.
void SDLRenderInterface::RenderGeometry(Rocket::Core::Vertex* vertices, int num_vertices, int* indices, int num_indices, const Rocket::Core::TextureHandle texture, const Rocket::Core::Vector2f& translation)
{
    GLuint program;
    GLuint vertexBuffer;
    GLuint indexBuffer;
    GLuint vertexPosLoc      = 0;
    GLuint vertexColorLoc    = 0;
    GLuint vertexTexCoordLoc = 0;
    GLuint texSamplerLoc     = 0;
    GLuint translationLoc    = 0;
    GLuint viewDimLoc        = 0;


    int offset = 8;
    int vertexCount = 4;
    float vertexData[] = {-0.5, -0.5, 1.0, 1.0, 1.0, 1.0, 0.0, 0.0,
                           0.5, -0.5, 1.0, 1.0, 1.0, 1.0, 1.0, 0.0,
                           0.5,  0.5, 1.0, 1.0, 1.0, 1.0, 1.0, 1.0,
                          -0.5,  0.5, 1.0, 1.0, 1.0, 1.0, 0.0, 1.0};
    int indexData[] = {0,1,2,0,2,3};
    int indexCount = 6;

    // Populate vertex buffer
    glGenBuffers(1, &vertexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
    glBufferData(GL_ARRAY_BUFFER, sizeof(float)*offset*vertexCount,
                 vertexData, GL_STATIC_DRAW);

    // Populate index buffer
    glGenBuffers(1, &indexBuffer);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(int) * indexCount,
                 indexData, GL_STATIC_DRAW);

    program = shaderManager->getProgram(2, "rocketTex.vert",
                                           "rocketTex.frag");
    glUseProgram(program);
    // Set up the texture
    texSamplerLoc = glGetUniformLocation(program, "texSampler");
    vertexTexCoordLoc = glGetAttribLocation(program, "vertexTexCoord");
    if(texSamplerLoc == -1)
    {
        std::cerr << "Error: cannot find texture location." << std::endl;
        return;
    }
    if(vertexTexCoordLoc == -1)
    {
        std::cerr << "Error: cannot find texture coord location."
                  << std::endl;
        return;
    }

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, (GLuint) texture);
    glUniform1i(texSamplerLoc, 0);

    // Set up the per vertex texture coords 
    glEnableVertexAttribArray(vertexTexCoordLoc);
    glVertexAttribPointer(vertexTexCoordLoc, 2, GL_FLOAT, GL_FALSE,
                          offset * sizeof(float),
                          (void*) (sizeof(float) * 6));

    // Set up uniforms
    translationLoc = glGetUniformLocation(program, "translation");
    viewDimLoc = glGetUniformLocation(program, "viewDimensions");
    if(translationLoc == -1)
    {
        std::cerr << "Error: cannot find translation location."
                  << std::endl;
        return;
    }
    if(viewDimLoc == -1)
    {
        std::cerr << "Error: cannot find viewDim location."
                  << std::endl;
        return;
    }
    glUniform2f(translationLoc, 0,0);
    glUniform2f(viewDimLoc, 1,1);


    // Set up per-vertex attributes
    vertexPosLoc = glGetAttribLocation(program, "vertexPosition");
    vertexColorLoc = glGetAttribLocation(program, "vertexColor");
    if(vertexPosLoc == -1)
    {
        std::cerr << "Error: cannot find vertex position location."
                  << std::endl;
        return;
    }
    if(vertexColorLoc == -1)
    {
        std::cerr << "Error: cannot find vertex color location."
                  << std::endl;
        return;
    }
    glEnableVertexAttribArray(vertexPosLoc);
    glEnableVertexAttribArray(vertexColorLoc);
    glVertexAttribPointer(vertexPosLoc, 2, GL_FLOAT, GL_FALSE,
                              offset * sizeof(float), 0);
    glVertexAttribPointer(vertexColorLoc, 4, GL_FLOAT, GL_TRUE,
                              offset * sizeof(float),
                              (void*) (sizeof(float) * 2));

    // Draw the geometry
    glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_INT, 0);

    glDisableVertexAttribArray(vertexPosLoc);
    glDisableVertexAttribArray(vertexColorLoc);
    glDisableVertexAttribArray(vertexTexCoordLoc);
    glDeleteBuffers(1, &vertexBuffer);
    glDeleteBuffers(1, &indexBuffer);
    glBindBuffer(GL_ARRAY_BUFFER, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
    glUseProgram(0);

}

顶点着色器:

#version 120

uniform vec2 translation;
uniform vec2 viewDimensions;

attribute vec2 vertexPosition;
attribute vec4 vertexColor;
attribute vec2 vertexTexCoord;

varying vec2 texCoord;
varying vec4 fragColor;

void main(void)
{
    vec2 ndcPos = ((vertexPosition + translation)/(viewDimensions));

    texCoord = vertexTexCoord;
    fragColor = vertexColor;
    gl_Position = vec4(ndcPos, 0.0, 1.0);
}

片段着色器:

#version 120

uniform sampler2D texSampler;

varying vec2 texCoord;
varying vec4 fragColor;

void main(void)
{
    vec4 objectColor = texture2D(texSampler, texCoord);
    gl_FragColor = vec4((objectColor * fragColor).xyz, 1.0);
}

Answer 1

所以，我终于想通了。 jozxyqk 关于测试纹理坐标的建议证实了我对纹理坐标不正确的怀疑(每个顶点都获得相同的坐标)。问题最终是我在我的代码的另一部分调用 glVertexAttribDivisor(attributeLoc, 1) 并且从未将它设置回每个顶点，所以它影响了我的其他着色器。考虑到 OpenGL 的设计，这是有必要的。

很高兴一切都解决了!