使用OpenGL 4.x的1d纹理进行纹理映射

Question

我想使用1d纹理（颜色渐变）来构造一个简单的三角形。

我的片段着色器看起来像这样：

#version 420

uniform sampler1D           colorRamp;
in float height;

out vec4 FragColor;

void main()
{
   FragColor = texture(colorRamp, height).rgba;
}

我的顶点着色器看起来像这样：

#version 420

layout(location = 0) in vec3 position;

out float height;

void main()
{
    height = (position.y + 0.75f) / (2 * 0.75f);
    gl_Position = vec4( position, 1.0);
}

绘制三角形时，我这样做（我删除了错误检查表单代码以获得更好的可读性）：

glUseProgram(program_);

GLuint samplerLocation = glGetUniformLocation(program_, name.toCString());
glUniform1i(samplerLocation, currentTextureUnit_);

glActiveTexture( GL_TEXTURE0 + currentTextureUnit_ );
glBindTexture(GL_TEXTURE_1D, textureId);

不幸的是我的三角形只是黑色。任何想法如何解决这个问题？

我很确定指定的纹理填充了适当的数据，因为我用glGetTexImage读回并检查了它。我是否需要调用其他函数来绑定和激活纹理？我有几乎相同的2d纹理代码，它正在工作。

当我以这种方式更改着色器代码时：

#version 420

uniform sampler1D           colorRamp;
in float height;

out vec4 FragColor;

void main()
{
   FragColor = vec4(height, height, height, 1.0); // change!
}

我得到这个输出：

我准备了一些重现错误的演示源代码。可以找到来源here。 它生成以下输出：

以这种方式创建1d纹理 - 只有红色像素：

static GLuint Create1DTexture()
{
    GLuint textureId_;

    // generate the specified number of texture objects 
    glGenTextures(1, &textureId_);
    assert(glGetError() == GL_NO_ERROR);

    // bind texture
    glBindTexture(GL_TEXTURE_1D, textureId_);
    assert(glGetError() == GL_NO_ERROR);

    // tells OpenGL how the data that is going to be uploaded is aligned
    glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
    assert(glGetError() == GL_NO_ERROR);

    float data[] =
    {
        1.0f, 0.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 0.0f, 1.0f,
        1.0f, 0.0f, 0.0f, 1.0f
    };

    glTexImage1D(
        GL_TEXTURE_1D,      // Specifies the target texture. Must be GL_TEXTURE_1D or GL_PROXY_TEXTURE_1D.
        0,                  // Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
        GL_RGBA32F,
        3*sizeof(float)*4,
        0,                  // border: This value must be 0.
        GL_RGBA,
        GL_FLOAT,
        data
    );
    assert(glGetError() == GL_NO_ERROR);

    // texture sampling/filtering operation.
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    assert(glGetError() == GL_NO_ERROR);
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_T, GL_REPEAT);
    assert(glGetError() == GL_NO_ERROR);
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
    assert(glGetError() == GL_NO_ERROR);
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    assert(glGetError() == GL_NO_ERROR);

    glBindTexture(GL_TEXTURE_1D, 0);
    assert(glGetError() == GL_NO_ERROR);

    return textureId_;
}

纹理绑定以这种方式完成：

GLuint samplerLocation = glGetUniformLocation(rc.ToonHandle, "ColorRamp");
glUniform1i(samplerLocation, 0);
glActiveTexture(GL_TEXTURE0 + 0);
glBindTexture(GL_TEXTURE_1D, rc.texure1d);

Answer 1

发现错误：

glTexImage1D(
    GL_TEXTURE_1D,      // Specifies the target texture. Must be GL_TEXTURE_1D or GL_PROXY_TEXTURE_1D.
    0,                  // Specifies the level-of-detail number. Level 0 is the base image level. Level n is the nth mipmap reduction image.
    GL_RGBA32F,
    3/*3*sizeof(float)*4*/,  // bug fix!!!!
    0,                  // border: This value must be 0.
    GL_RGBA,
    GL_FLOAT,
    data
);