1、glBufferData

  1. std::vector<Vertex> mVertices;
  3. glGenVertexArrays( 1, &mVAO );
  4. glGenBuffers( 1, &mVBO );
  5. glBindVertexArray( mVAO );
  7. glBindBuffer( GL_ARRAY_BUFFER, mVBO );
  8. glBufferData( GL_ARRAY_BUFFER, 
  9.              mVertices.size() * sizeof( Vertex ),
  10.              &mVertices[0],                            // ！！！这里不是&mVertices
  11.              GL_STATIC_DRAW );
  13. glEnableVertexAttribArray( 0 );
  14. glVertexAttribPointer( 0,
  15.                       3,
  16.                       GL_FLOAT,
  17.                       GL_FALSE,
  18.                       sizeof( Vertex ),
  19.                       ( void * ) 0 );                // 正确写法应该是( void * ) (0 * sizeof(GLfloat))，假设元素为GLfloat类型
  21. glBindVertexArray( 0 );

2、glUseProgram

  2. //shader.use();        // 忘记调用glUseProgram，导致着色器并没有被使用
  4. shader.setInt( "task", TASK_COORD );
  5. shader.setMat4( "modelMatrix", glm::mat4( 1.0f ) );
  6. shader.setMat4( "viewMatrix", viewMatrix );
  7. shader.setMat4( "projectionMatrix", projectionMatrix );
  8. glBindVertexArray( VAO_coord );
  9. glDrawArrays( GL_LINES, 0, 6 );

3、glEnableVertexAttribArray

  2. const GLfloat pos[] = { ... };
  3. const GLfloat normal[] = { ... };
  4. const GLfloat tex[] = { ... };
  6. glGenBuffers( 1, VBO );             // 创建VBO
  7. glBindBuffer( GL_ARRAY_BUFFER, *VBO );
  8. glBufferData( GL_ARRAY_BUFFER, len, vertices, GL_STATIC_DRAW );     // 填充数据
  10. // 填充缓冲
  11. glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(positions), &positions);
  12. glBufferSubData(GL_ARRAY_BUFFER, sizeof(positions), sizeof(normals), &normals);
  13. glBufferSubData(GL_ARRAY_BUFFER, sizeof(positions) + sizeof(normals), sizeof(tex), &tex);
  15. glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), 0);  
  16. glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)(sizeof(positions)));  
  17. glVertexAttribPointer(2, 2, GL_FLOAT, GL_FALSE, 2 * sizeof(float), (void*)(sizeof(positions) + sizeof(normals)));
  19. glEnableVertexAttribArray( 0 );        // 特别容易漏掉这个
  20. glEnableVertexAttribArray( 1 );
  21. glEnableVertexAttribArray( 2 );

4、着色器中的奇怪问题

下面是一个几何着色器。
项目链接：https://github.com/JackieLong/OpenGL/tree/main/project_geometry_shader_test

  2. #version 330 core
  4. layout(triangles) in;
  5. layout(triangle_strip, max_vertices = 3) out;
  7. in vec2 texCoord[];
  9. uniform float time;
  11. out vec2 outTexCoord;
  13. vec4 explode(vec4 pos, vec3 normal);
  14. vec3 triangleNormal(); 
  16. void main() {
  18.     vec3 normal = triangleNormal();
  20.     // 如果用注释的代码，结果就异常，没有加载出模型
  22.     gl_Position = explode(vec4(gl_in[0].gl_Position), normal);
  23.     // gl_Position = explode(gl_in[0].gl_Position, normal);
  24.     outTexCoord = texCoord[0];
  25.     EmitVertex();
  27.     gl_Position = explode(vec4(gl_in[1].gl_Position), normal);
  28.     // gl_Position = explode(gl_in[1].gl_Position, normal);
  29.     outTexCoord = texCoord[1];
  30.     EmitVertex();
  32.     gl_Position = explode(vec4(gl_in[2].gl_Position), normal);
  33.     // gl_Position = explode(gl_in[2].gl_Position, normal);
  34.     outTexCoord = texCoord[2];
  35.     EmitVertex();
  37.     EndPrimitive();
  38. }
  40. vec4 explode(vec4 pos, vec3 normal)
  41. {
  42.     return pos + vec4(normal * ((1.0 + sin(time)) / 2.0), 0.0);
  43. }
  45. vec3 triangleNormal()
  46. {
  47.     vec3 fuck1 = vec3(gl_in[0].gl_Position - gl_in[1].gl_Position);
  48.     vec3 fuck2 = vec3(gl_in[2].gl_Position - gl_in[1].gl_Position);
  49.     return normalize(cross(fuck1, fuck2));
  50. }