我正在尝试在openGL中实现一个天空盒但是由于某种原因它没有被正确绘制，除非我关闭了背面剔除，甚至它显示了3个被搞砸的三角形。 Maby我不是画三角形，但我不确定。
bool Skybox::onInitialize()
{
myRadius = 100;
setPosition(Vector3(0.0f, 0.0f, 0.0f));
//Initialize color matrix
myColors.push_back(Color(1.0f, 0.0f, 0.0f, 1.0f));
myColors.push_back(Color(1.0f, 1.0f, 0.0f, 1.0f));
myColors.push_back(Color(1.0f, 0.5f, 0.0f, 1.0f));
myColors.push_back(Color(0.5f, 0.5f, 0.5f, 1.0f));
//Position the key points of the cube
myVertices.push_back(Vertex(-myRadius, -myRadius, myRadius));//0
myVertices.push_back(Vertex(-myRadius, -myRadius, -myRadius));//1
myVertices.push_back(Vertex(myRadius, -myRadius, -myRadius));//2
myVertices.push_back(Vertex(myRadius, -myRadius, myRadius));//3
myVertices.push_back(Vertex(-myRadius, myRadius, myRadius));//4
myVertices.push_back(Vertex(-myRadius, myRadius, -myRadius));//5
myVertices.push_back(Vertex( myRadius, myRadius, -myRadius));//6
myVertices.push_back(Vertex( myRadius, myRadius, myRadius));//7
//Push back the indices that make up the triangles for each face.
//Bottom
myIndices.push_back(0);
myIndices.push_back(1);
myIndices.push_back(2);
myIndices.push_back(2);
myIndices.push_back(1);
myIndices.push_back(0);
//Top
myIndices.push_back(7);
myIndices.push_back(6);
myIndices.push_back(4);
myIndices.push_back(6);
myIndices.push_back(5);
myIndices.push_back(4);
//Left
myIndices.push_back(0);
myIndices.push_back(4);
myIndices.push_back(1);
myIndices.push_back(4);
myIndices.push_back(5);
myIndices.push_back(1);
//Right
myIndices.push_back(2);
myIndices.push_back(6);
myIndices.push_back(3);
myIndices.push_back(6);
myIndices.push_back(7);
myIndices.push_back(3);
//Back
myIndices.push_back(6);
myIndices.push_back(1);
myIndices.push_back(5);
myIndices.push_back(6);
myIndices.push_back(2);
myIndices.push_back(1);
//Front
myIndices.push_back(0);
myIndices.push_back(7);
myIndices.push_back(4);
myIndices.push_back(0);
myIndices.push_back(3);
myIndices.push_back(7);
//Generate Texture Coordinates
//Bottom
myTexCoords.push_back(TexCoord(0.25, 0));
myTexCoords.push_back(TexCoord(0.25, 0.375));
myTexCoords.push_back(TexCoord(0.5, 0.375));
myTexCoords.push_back(TexCoord(0.5, 0));
//Top
myTexCoords.push_back(TexCoord(0.25, 1));
myTexCoords.push_back(TexCoord(0.25, 0.625));
myTexCoords.push_back(TexCoord(0.5, 0.625));
myTexCoords.push_back(TexCoord(0.5, 1));
//Left
myTexCoords.push_back(TexCoord(0, 0.625));
myTexCoords.push_back(TexCoord(0.25, 0.625));
myTexCoords.push_back(TexCoord(0.25, 0.375));
myTexCoords.push_back(TexCoord(0, 0.375));
//Right
myTexCoords.push_back(TexCoord(0.5, 0.625));
myTexCoords.push_back(TexCoord(0.75, 0.625));
myTexCoords.push_back(TexCoord(0.75, 0.375));
myTexCoords.push_back(TexCoord(0.5, 0.375));
//Back
myTexCoords.push_back(TexCoord(0.75, 0.625));
myTexCoords.push_back(TexCoord(1.0, 0.625));
myTexCoords.push_back(TexCoord(1.0, 0.375));
myTexCoords.push_back(TexCoord(0.75, 0.375));
const string vertexShader = (GLSLProgram::glsl130Supported()) ? VERTEX_SHADER_130 : VERTEX_SHADER_120;
const string fragmentShader = (GLSLProgram::glsl130Supported()) ? FRAGMENT_SHADER_130 : FRAGMENT_SHADER_120;
if (!myTexture.load(SKY_TEXTURE))
{
std::cerr << "Could not load the particle texture" << std::endl;
return false;
}
glGenTextures(1, &myTexID);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, myTexID);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, myTexture.getWidth(),
myTexture.getHeight(), 0, GL_RGBA, GL_UNSIGNED_BYTE,
myTexture.getImageData());
m_shaderProgram = std::auto_ptr<GLSLProgram>(new GLSLProgram(vertexShader, fragmentShader));
if (!m_shaderProgram->initialize())
{
std::cerr << "Could not load the skybox shaders" << std::endl;
return false;
}
m_shaderProgram->bindAttrib(0, "a_Vertex");
m_shaderProgram->bindAttrib(1, "a_Color");
m_shaderProgram->bindAttrib(2, "a_TexCoord0");
m_shaderProgram->linkProgram();
m_shaderProgram->sendUniform("texture0", 0);
glGenBuffers(1, &myVertexBuffer); //Generate a buffer for the vertices
glBindBuffer(GL_ARRAY_BUFFER, myVertexBuffer); //Bind the vertex buffer
glBufferData(GL_ARRAY_BUFFER, sizeof(Vector3) * myVertices.size(), &myVertices[0], GL_STATIC_DRAW); //Send the data to OpenGL
glGenBuffers(1, &myColorBuffer);
glBindBuffer(GL_ARRAY_BUFFER, myColorBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(Color) * myColors.size(), &myColors[0], GL_STATIC_DRAW); //Send the data to OpenGL
glGenBuffers(1, &myTexCoordBuffer);
glBindBuffer(GL_ARRAY_BUFFER, myTexCoordBuffer);
glBufferData(GL_ARRAY_BUFFER, sizeof(TexCoord) * myTexCoords.size(), &myTexCoords[0], GL_STATIC_DRAW); //Send the data to OpenGL
glGenBuffers(1, &myIndexBuffer);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, myIndexBuffer); //Bind the vertex buffer
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(GLuint) * myIndices.size(), &myIndices[0], GL_STATIC_DRAW); //Send the data to OpenGL
return true;
}
void Skybox::onRender() const
{
//glDisable(GL_DEPTH_TEST);
//glPushMatrix();
glTranslatef(0.0f, 0.0f, 0.0f);
static float modelviewMatrix[16];
static float projectionMatrix[16];
m_shaderProgram->bindShader();
//Get the current matrices from OpenGL
glGetFloatv(GL_MODELVIEW_MATRIX, modelviewMatrix);
glGetFloatv(GL_PROJECTION_MATRIX, projectionMatrix);
//Enable the point sprite and the automatic texture coordinates
glBindTexture(GL_TEXTURE_2D, myTexID);
glEnableVertexAttribArray(0);
glEnableVertexAttribArray(1);
glEnableVertexAttribArray(2);
//Send the modelview and projection matrices to the shaders
m_shaderProgram->sendUniform4x4("modelview_matrix", modelviewMatrix);
m_shaderProgram->sendUniform4x4("projection_matrix", projectionMatrix);
m_shaderProgram->sendUniform("texture0", 0);
//Bind the vertex array and set the vertex pointer to point at it
glBindBuffer(GL_ARRAY_BUFFER, myVertexBuffer);
glVertexAttribPointer((GLint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ARRAY_BUFFER, myColorBuffer);
glVertexAttribPointer((GLint)1, 4, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ARRAY_BUFFER, myTexCoordBuffer);
glVertexAttribPointer((GLint)2, 2, GL_FLOAT, GL_FALSE, 0, 0);
//Bind the index array
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, myIndexBuffer);
//glDrawElements(GL_TRIANGLES, myIndices.size(), GL_UNSIGNED_INT, 0);
glPointSize(5.0f);
glDrawArrays(GL_TRIANGLES, 0, myIndices.size());
glDisableVertexAttribArray(2);
glDisableVertexAttribArray(1);
glDisableVertexAttribArray(0);
// glPopMatrix();
}
答案 0 :(得分：1)
您的绘图代码非常混乱。它有很多问题，但它们都源于一个基本的误解。
您有4种颜色，8个位置和24个纹理坐标。 OpenGL不知道如何处理它。
OpenGL只能使用唯一的顶点属性组。因此，如果您有位置和纹理坐标，则这些数组的长度必须相等。对于每个纹理坐标，都有一个与之配对的特定位置，反之亦然。对于每个位置，都有一种与之配对的特定颜色，反之亦然。
是的，一个立方体只有8个不同的位置。但是你没有绘制8个顶点（顶点是属性数据的集合，如果你愿意，可能包含一个位置）。你正在绘制12个三角形。每个三角形有3个顶点。
如果三角形共享该顶点的顶点属性的所有，则它们只能共享顶点。因此，立方体的一个面可以由四个角顶点表示，因为两个三角形（沿着主对角线）共享两个共享顶点的相同位置/颜色/ texCoord。
但是，如果不同面的三角形使用相同的位置/颜色/ texCoord三元组，则它们只能共享顶点数据。在大多数情况下，你的不会。
因此，你必须复制你的位置和颜色。立方体的每个面都将具有单独的位置和颜色（即使它们可能使用与其他人相同的值）。
另外，请考虑完全避免纹理坐标。您显然使用着色器，因此只需将环境放在立方体贴图中即可。您可以在从立方体贴图向外指向的8个角处传递“法线”。将它们作为标准插值，然后使用它们访问立方体贴图纹理。