如何在现代 opengl 中制作示例 1D 纹理？

Question

我创建了这个简单的程序。它创建了两个纹理，一个 2D 和一个 1D 纹理绑定它们，等等。

我可以毫无问题地在我的着色器程序中对 2D 纹理进行采样和绘制。尝试从 1D 纹理中采样和绘制，四边形变成黑色。

如果我不在 if..else.. 语句中的片段着色器中使用 1D 纹理样本，则所有内容都会呈现为黑白。尝试使用示例，它只呈现黑屏。

如果我这样做：

if (i == maxIterations)
    {
       tcolor = vec4(0.0f, 0.0f, 0.0f, 1.0f);
    }
    else if(i <= 10)
    {
        tcolor = vec4(1.0f, 0.0f, 0.0f, 0.0f);

    } else if ( i >= 11)
    {
        tcolor = vec4(1.0f, 1.0f, 0.0f, 0.0f);
    }

它也有效.....如何对 1D 纹理进行采样？

源代码如下

    glGenTextures(1, &colorTextureID);
    glBindTexture(GL_TEXTURE_2D, colorTextureID);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


    glTexImage2D(GL_TEXTURE_2D, 0, Mode, colorSurface->w, colorSurface->h, 0, Mode, GL_UNSIGNED_BYTE, colorSurface->pixels);
    glGenerateMipmap(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, 0);
    free(colorSurface);

    //mandi 1d texture
    glGenTextures(1, &mandiTextureID);
    glBindTexture(GL_TEXTURE_1D, mandiTextureID);

    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_S, GL_REPEAT);
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_WRAP_T, GL_REPEAT);

    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
    glTexParameteri(GL_TEXTURE_1D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);


    glTexImage1D(GL_TEXTURE_1D, 0, Mode1, mandiSurface->w, 0, Mode1, GL_UNSIGNED_BYTE, mandiSurface->pixels);
    glBindTexture(GL_TEXTURE_1D, 0);
    free(mandiSurface);

    //render
    void render()
{
    glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

    //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
    glUseProgram(sp);

    glActiveTexture(GL_TEXTURE0);
    glBindTexture(GL_TEXTURE_2D, colorTextureID);//ourTexture
    ourTexture = getUniformLocation(sp, "ourTexture");
    glUniform1i(ourTexture, 0);

    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_1D, mandiTextureID);//mandiTexture
    mandiTexture = getUniformLocation(sp, "mandiTexture");
    glUniform1i(mandiTexture, 1);


    glBindVertexArray(verticesBuffer);
    viewMat = getUniformLocation(sp, "viewMat");
    modelMat = getUniformLocation(sp, "modelMat");
    projMat = getUniformLocation(sp, "projMat");

    maxIterLoc = getUniformLocation(sp, "maxIterations");
    centerLoc = getUniformLocation(sp, "center");
    scaleLoc = getUniformLocation(sp, "scale");

    glUniformMatrix4fv(viewMat, 1, GL_FALSE, vm.m);
    glUniformMatrix4fv(projMat, 1, GL_FALSE, opm.m);
    glUniformMatrix4fv(modelMat, 1, GL_FALSE, tm.m);

    glUniform1i(maxIterLoc, 20);
    glUniform1f(scaleLoc, scale);
    glUniform2f(centerLoc, cx, cy);

    glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
}

顶点着色器

#version 330 core

layout (location = 0) in vec3 position;
layout (location = 1) in vec3 icolor;
layout (location = 2) in vec2 vTexCoord;

uniform mat4 modelMat;
uniform mat4 viewMat;
uniform mat4 projMat;

out vec4 fcolor;
out vec2 fTexCoord;
out vec2 fCoord;

void main()
{
    gl_Position =  projMat * viewMat * modelMat * vec4(position, 1.0);

    fCoord = vec2(position);
    fTexCoord = vTexCoord;
    fcolor = vec4(icolor, 1.0f);
}

片段着色器

#version 330 core

in vec4 fcolor;
in vec2 fTexCoord;
in vec2 fCoord;

uniform int maxIterations;
uniform vec2 center;
uniform float scale;

uniform sampler2D ourTexture;
uniform sampler1D mandiTexture;

out vec4 color;

void main()
{
   vec2 c, z;

    c.x = 1.3333 * (fCoord.x - 0.5) - center.x;
    c.y = (fCoord.y - 0.5) - center.y;

        int i;
        z = c;
        for(i=0; i<maxIterations; i++) {
            float x = (z.x * z.x - z.y * z.y) + c.x;
            float y = (z.y * z.x + z.x * z.y) + c.y;

            if((x * x + y * y) > 4.0) break;
            z.x = x;
            z.y = y;
        }

    vec4 tcolor;

    if (i == maxIterations)
    {
       tcolor = vec4(0.0f, 0.0f, 0.0f, 1.0f);
    }
    else
    {
       /* tcolor = vec4(1.0f, 1.0f, 1.0f, 1.0f);  this works but only renders black and white */
       tcolor = texture(mandiTexture, float(i)).rgba; /* only renders black screen */
    }

    /* color = texture(ourTexture, fTexCoord) * fcolor; //this also works */
    color = tcolor;
}

Answer 1

目前，您正在使用 0 到 maxIterations（i 的可能值）范围内的纹理坐标来查找 1D 纹理中的值。正如 dari 在评论中提到的，纹理坐标在 0-1 的范围内，忽略了 wrap 和 Clamp。

所以，将i 除以maxIterations 得到0-1 范围内的坐标：

tcolor = texture(mandiTexture, float(i) / float(maxIterations)).rgba;