Question

我有两种测试代码的方法。第一个使用单个 VBO，顶点和纹理坐标交织在一起，在窗口中绘制一个正方形。第二个使用三个 VBO 的数组来定义顶点、纹理坐标和颜色值。

第一种方法成功地将一个黑色方块渲染到窗口的中心。第二种方法不渲染任何东西。我开始使用 RenderDoc 进行故障排除，发现在“网格查看器”选项卡下，第一个方法的 glDrawArrays() 调用列出了顶点和纹理坐标。当检查第二个方法的 glDrawArrays() 调用时，所有传递的值都是 0。

谁能向我解释为什么会发生这种情况以及如何解决？

第一种方法：

public static void GenDrawQuad() {
        int quadVAO = 0;
        int quadVBO = 0;

        float vertices[] = {
                // Positions         Texcoords
                -0.5f,  0.5f, 0.0f,  -0.5f, 0.5f,
                -0.5f, -0.5f, 0.0f,  -0.5f,-0.5f,
                0.5f,  0.5f, 0.0f,   0.5f, 1.5f,
                0.5f, -0.5f, 0.0f,   0.5f,-0.5f,
        };

        // Gen VAO to contain VBO
        quadVAO = glGenVertexArrays();
        glBindVertexArray(quadVAO);

        // Gen and fill vertex buffer (VBO)
        quadVBO = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO);
        glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW);

        // Bind vertex attributes (position, texcoords)
        glEnableVertexAttribArray(0);
        glVertexAttribPointer(0, 3, GL_FLOAT, false, 5*Float.BYTES,0); //Positions
        glEnableVertexAttribArray(1);
        glVertexAttribPointer(1, 2, GL_FLOAT, false, 5*Float.BYTES,3*Float.BYTES); //Texcoords

        // Draw quad
        glBindVertexArray(quadVAO);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
        glBindVertexArray(0);

        // Delete buffers (VBO and VAO)
        glDeleteBuffers(quadVBO);
        glDeleteVertexArrays(quadVAO);
    }

第一种方法的RenderDoc：

第二种方法：

public static void GenDrawQuadAlt() {
        int quadVAO = 0;
        int[] quadVBO = {0, 0, 0};
        Shader shaderProgram = GetShaderDefault();

        float vertices[] = {
                // Positions
                -0.5f,  0.5f, 0.0f,
                -0.5f, -0.5f, 0.0f,
                 0.5f,  0.5f, 0.0f,
                 0.5f, -0.5f, 0.0f
        };

        float[] texcoords = {
                 0.5f, -0.5f,
                -0.5f, -0.5f,
                 0.5f,  0.5f,
                 0.5f, -0.5f
        };

        float[] colour = {
                255, 109, 154, 255,
                255, 109, 154, 255,
                255, 109, 154, 255,
                255, 109, 154, 255
        };

        // Gen VAO to contain VBO
        quadVAO = glGenVertexArrays();
        glBindVertexArray(quadVAO);

        // Gen and fill vertex buffer (VBO)
        quadVBO[0] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[0]);
        glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW);

        quadVBO[1] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[1]);
        glBufferData(GL_ARRAY_BUFFER, texcoords, GL_STATIC_DRAW);

        quadVBO[2] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[2]);
        glBufferData(GL_ARRAY_BUFFER, colour, GL_STATIC_DRAW);

        // Bind vertex attributes (position, texcoords)
        glEnableVertexAttribArray(shaderProgram.getLocs().get(LOC_VERTEX_POSITION.ShaderLocationInt));
        glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_POSITION.ShaderLocationInt), 3, GL_FLOAT,
                false, 0,0); //Positions

        glEnableVertexAttribArray(shaderProgram.getLocs().get(LOC_VERTEX_TEXCOORD01.ShaderLocationInt));
        glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_TEXCOORD01.ShaderLocationInt), 2, GL_FLOAT,
                false, 0,0); //Texcoords

        glEnableVertexAttribArray(shaderProgram.getLocs().get(LOC_VERTEX_COLOR.ShaderLocationInt));
        glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_COLOR.ShaderLocationInt), 4, GL_FLOAT,
                false, 0, 0); //Colours

        // Draw quad
        glUseProgram(shaderProgram.getId());
        glBindVertexArray(quadVAO);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
        glBindVertexArray(0);
        glUseProgram(0);

        // Delete buffers (VBO and VAO)
        glDeleteBuffers(quadVBO);
        glDeleteVertexArrays(quadVAO);
    }

第二种方法的RenderDoc：

::EDIT::

经过一番修改后，我现在有了以下方法，它将值放置在我的着色器的预期位置并为我提供 gl_Position 输出，但不会渲染到屏幕上。

public static void GenDrawQuadAlt() {
        int quadVAO = 0;
        int[] quadVBO = {0, 0, 0, 0};
        Shader shaderProgram = rlglData.getState().getCurrentShader();

        float vertices[] = {
                -0.5f,  0.5f, 0.0f,
                -0.5f, -0.5f, 0.0f,
                0.5f,  0.5f, 0.0f,
                0.5f, -0.5f, 0.0f
        };

        float[] texcoords = {
                0.5f, -0.5f,
                -0.5f, -0.5f,
                0.5f,  0.5f,
                0.5f, -0.5f
        };

        float[] colour = {
                255, 109, 154, 255,
                255, 109, 154, 255,
                255, 109, 154, 255,
                255, 109, 154, 255
        };

        int[] indices = {
                0, 1, 2,
                0, 2, 3
        };

        // Gen VAO to contain VBO
        quadVAO = glGenVertexArrays();
        glBindVertexArray(quadVAO);

        // Gen and fill vertex buffer (VBO)
        quadVBO[0] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[0]);
        glBufferData(GL_ARRAY_BUFFER, vertices, GL_STATIC_DRAW);
        glVertexAttribPointer(0, 3, GL_FLOAT,
                false, 0,0); //Positions
        glEnableVertexAttribArray(0);

        quadVBO[1] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[1]);
        glBufferData(GL_ARRAY_BUFFER, texcoords, GL_STATIC_DRAW);
        glVertexAttribPointer(1, 2, GL_FLOAT,
                false, 0,0); //Texcoords
        glEnableVertexAttribArray(1);

        quadVBO[2] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[2]);
        glBufferData(GL_ARRAY_BUFFER, colour, GL_STATIC_DRAW);
        glVertexAttribPointer(3, 4, GL_FLOAT,
                false, 0, 0); //Colours
        glEnableVertexAttribArray(3);

        quadVBO[3] = glGenBuffers();
        glBindBuffer(GL_ARRAY_BUFFER, quadVBO[3]);
        glBufferData(GL_ARRAY_BUFFER, indices, GL_STATIC_DRAW);

        // Draw quad
        glUseProgram(shaderProgram.getId());
        glBindVertexArray(quadVAO);
        glDrawArrays(GL_TRIANGLE_STRIP, 0, vertices.length/3);
        glBindVertexArray(0);
        glUseProgram(0);

        // Delete buffers (VBO and VAO)
        glDeleteBuffers(quadVBO);
        glDeleteVertexArrays(quadVAO);
    }

我的顶点着色器：

#version 330                       
in vec3 vertexPosition;            
in vec2 vertexTexCoord;            
in vec4 vertexColor;               
out vec2 fragTexCoord;             
out vec4 fragColor;                
uniform mat4 mvp;                  
void main()                        
{                                  
    fragTexCoord = vertexTexCoord; 
    fragColor = vertexColor;       
    gl_Position = vec4(vertexPosition.x, vertexPosition.y, vertexPosition.z, 1.0); 
}

我的片段着色器：

#version 330       
in vec2 fragTexCoord;              
in vec4 fragColor;                 
out vec4 finalColor;               
uniform sampler2D texture0;        
uniform vec4 colDiffuse;           
void main()                        
{                                  
    vec4 texelColor = texture(texture0, fragTexCoord);   
    finalColor = texelColor*colDiffuse*fragColor;        
}

Answer 1

glVertexAttribPointer 将实际绑定到 GL_ARRAY_BUFFER 目标的缓冲区对象与属性相关联。您必须在调用 glVertexAttribPointer 之前绑定缓冲区对象：

glBindBuffer(GL_ARRAY_BUFFER, quadVBO[0]);
glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_POSITION.ShaderLocationInt), 3, GL_FLOAT,
                false, 0,0); //Positions

glBindBuffer(GL_ARRAY_BUFFER, quadVBO[1]);
glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_TEXCOORD01.ShaderLocationInt), 2, GL_FLOAT,
                false, 0,0); //Texcoords

glBindBuffer(GL_ARRAY_BUFFER, quadVBO[3]);
glVertexAttribPointer(shaderProgram.getLocs().get(LOC_VERTEX_COLOR.ShaderLocationInt), 4, GL_FLOAT,
                false, 0, 0); //Colours

Answer 2

使用 glGetUniformLocation() 设置着色器属性后，我发现由于着色器构造函数中的错误，未定义着色器位置值。一旦我纠正了这个错误，我的四边形就会被绘制到屏幕上。

感谢所有的帮助和投入！

Answer 3

您正在将位置、uv、颜色缓冲到三个不同的缓冲区，它们都指向 GL_ARRAY_BUFFER 目标。您一次只能与一个目标 + 缓冲区组合进行绘制/交互。此外，您在 glVertexAttribpointer

中缺少正确的步幅

您需要像处理第一个数据一样组合您的顶点数据：

      float vertices[] = {
                // Positions         Texcoords     color
                -0.5f,  0.5f, 0.0f,  -0.5f, 0.5f,  255, 109, 154, 255,

然后在这里使用正确的步幅：

glVertexAttribPointer(0, 3, GL_FLOAT, false, 9*Float.BYTES, 0); // positions
glVertexAttribPointer(1, 2, GL_FLOAT, false, 9*Float.BYTES, 3*Float.BYTES); // texcoords
glVertexAttribPointer(2, 4, GL_FLOAT, false, 9*Float.BYTES, 5*Float.BYTES); // color

着色器不渲染到窗口

3 个答案: