我是OpenGl的新手，正在从事纹理设计。我想在立方体的三个面上绘制一个图像，在立方体的其他三个面上绘制另一个图像。我做不到我想知道我的代码在窗口的哪个位置绘制了立方体？
这是我的代码：
#include "06_texturing.hpp"
#include "texture.hpp"
GLuint shaderProgram;
GLuint vbo[2], vao[2];
GLuint tex;
glm::mat4 rotation_matrix;
glm::mat4 projection_matrix;
glm::mat4 c_rotation_matrix;
glm::mat4 lookat_matrix;
glm::mat4 model_matrix;
glm::mat4 view_matrix;
glm::mat4 modelview_matrix;
glm::mat3 normal_matrix;
GLuint uModelViewMatrix;
GLuint viewMatrix;
GLuint normalMatrix;
//-----------------------------------------------------------------
//6 faces, 2 triangles/face, 3 vertices/triangle
const int num_vertices = 36;
glm::vec4 texCoordinates[8];
//Eight vertices in homogenous coordinates
glm::vec4 positions[8] = {
glm::vec4(-0.5, -0.5, 0.5, 1.0),
glm::vec4(-0.5, 0.5, 0.5, 1.0),
glm::vec4(0.5, 0.5, 0.5, 1.0),
glm::vec4(0.5, -0.5, 0.5, 1.0),
glm::vec4(-0.5, -0.5, -0.5, 1.0),
glm::vec4(-0.5, 0.5, -0.5, 1.0),
glm::vec4(0.5, 0.5, -0.5, 1.0),
glm::vec4(0.5, -0.5, -0.5, 1.0)
};
glm::vec4 normals[8] = {
glm::vec4(-0.5, -0.5, 0.5, 1.0),
glm::vec4(-0.5, 0.5, 0.5, 1.0),
glm::vec4(0.5, 0.5, 0.5, 1.0),
glm::vec4(0.5, -0.5, 0.5, 1.0),
glm::vec4(-0.5, -0.5, -0.5, 1.0),
glm::vec4(-0.5, 0.5, -0.5, 1.0),
glm::vec4(0.5, 0.5, -0.5, 1.0),
glm::vec4(0.5, -0.5, -0.5, 1.0)
};
//RGBA colors
glm::vec4 colors[8] = {
glm::vec4(0.0, 0.0, 0.0, 1.0),
glm::vec4(1.0, 0.0, 0.0, 1.0),
glm::vec4(1.0, 1.0, 0.0, 1.0),
glm::vec4(0.0, 1.0, 0.0, 1.0),
glm::vec4(0.0, 0.0, 1.0, 1.0),
glm::vec4(1.0, 0.0, 1.0, 1.0),
glm::vec4(1.0, 1.0, 1.0, 1.0),
glm::vec4(0.0, 1.0, 1.0, 1.0)
};
glm::vec2 t_coords[4] = {
glm::vec2( 0.0, 0.0),
glm::vec2( 0.0, 1.0),
glm::vec2( 1.0, 0.0),
glm::vec2( 1.0, 1.0)
};
glm::vec4 color(0.6, 0.6, 0.6, 1.0);
glm::vec4 black(0.1, 0.1, 0.1, 1.0);
glm::vec4 white(0.2, 0.7, 0.7, 1.0);
glm::vec4 red(1.0, 0.2, 0.2, 1.0);
glm::vec4 yellow(0.8, 0.8, 0.0, 1.0);
glm::vec4 green(0.2, 0.7, 0.2, 1.0);
glm::vec4 blue(0.2, 0.2, 0.7, 1.0);
int tri_idx=0;
glm::vec4 v_positions[num_vertices];
glm::vec4 v_colors[num_vertices];
glm::vec4 v_normals[num_vertices];
glm::vec2 tex_coords[num_vertices];
// quad generates two triangles for each face and assigns colors to the vertices
void quad(int a, int b, int c, int d, glm::vec4 color)
{
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[a];
v_normals[tri_idx] = normals[a];
tex_coords[tri_idx] = t_coords[1];
tri_idx++;
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[b];
v_normals[tri_idx] = normals[b];
tex_coords[tri_idx] = t_coords[0];
tri_idx++;
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[c];
v_normals[tri_idx] = normals[c];
tex_coords[tri_idx] = t_coords[2];
tri_idx++;
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[a];
v_normals[tri_idx] = normals[a];
tex_coords[tri_idx] = t_coords[1];
tri_idx++;
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[c];
v_normals[tri_idx] = normals[c];
tex_coords[tri_idx] = t_coords[2];
tri_idx++;
v_colors[tri_idx] = color; v_positions[tri_idx] = positions[d];
v_normals[tri_idx] = normals[d];
tex_coords[tri_idx] = t_coords[3];
tri_idx++;
}
// generate 12 triangles: 36 vertices and 36 colors
void colorcube(void)
{
quad( 1, 0, 3, 2, red);
quad( 2, 3, 7, 6, green);
quad( 3, 0, 4, 7, white);
quad( 6, 5, 1, 2, yellow);
quad( 4, 5, 6, 7, black);
quad( 5, 4, 0, 1, blue);
}
//-----------------------------------------------------------------
void initBuffersGL(void)
{
// Load shaders and use the resulting shader program
std::string vertex_shader_file("06_vshader.glsl");
std::string fragment_shader_file("06_fshader.glsl");
std::vector<GLuint> shaderList;
shaderList.push_back(csX75::LoadShaderGL(GL_VERTEX_SHADER, vertex_shader_file));
shaderList.push_back(csX75::LoadShaderGL(GL_FRAGMENT_SHADER, fragment_shader_file));
shaderProgram = csX75::CreateProgramGL(shaderList);
glUseProgram( shaderProgram );
// getting the attributes from the shader program
GLuint vPosition = glGetAttribLocation( shaderProgram, "vPosition" );
GLuint vColor = glGetAttribLocation( shaderProgram, "vColor" );
GLuint vNormal = glGetAttribLocation( shaderProgram, "vNormal" );
GLuint texCoord = glGetAttribLocation( shaderProgram, "texCoord" );
uModelViewMatrix = glGetUniformLocation( shaderProgram, "uModelViewMatrix");
normalMatrix = glGetUniformLocation( shaderProgram, "normalMatrix");
viewMatrix = glGetUniformLocation( shaderProgram, "viewMatrix");
// Load Textures
GLuint tex=LoadTexture("images/all1.bmp",256,256);
GLuint tex2=LoadTexture("images/another.bmp",256,256);
glBindTexture(GL_TEXTURE_2D, tex);
//Ask GL for two Vertex Attribute Objects (vao) , one for the sphere and one for the wireframe
glGenVertexArrays (2, vao);
//Ask GL for two Vertex Buffer Object (vbo)
glGenBuffers (2, vbo);
//Set 0 as the current array to be used by binding it
glBindVertexArray (vao[0]);
//Set 0 as the current buffer to be used by binding it
glBindBuffer (GL_ARRAY_BUFFER, vbo[0]);
colorcube();
//Copy the points into the current buffer
glBufferData (GL_ARRAY_BUFFER, sizeof (v_positions) + sizeof(tex_coords) + sizeof(v_normals), NULL, GL_STATIC_DRAW);
glBufferSubData( GL_ARRAY_BUFFER, 0, sizeof(v_positions), v_positions );
glBufferSubData( GL_ARRAY_BUFFER, sizeof(v_positions), sizeof(tex_coords), tex_coords);
glBufferSubData( GL_ARRAY_BUFFER, sizeof(tex_coords)+sizeof(v_positions), sizeof(v_normals), v_normals );
// set up vertex array
//Position
glEnableVertexAttribArray( vPosition );
glVertexAttribPointer( vPosition, 4, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(0) );
//Textures
glEnableVertexAttribArray( texCoord );
glVertexAttribPointer( texCoord, 2, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(sizeof(v_positions)) );
//Normal
glEnableVertexAttribArray( vNormal );
glVertexAttribPointer( vNormal, 3, GL_FLOAT, GL_FALSE, 0, BUFFER_OFFSET(sizeof(v_positions)+sizeof(tex_coords)) );
}
void renderGL(void)
{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
rotation_matrix = glm::rotate(glm::mat4(1.0f), glm::radians(xrot), glm::vec3(1.0f,0.0f,0.0f));
rotation_matrix = glm::rotate(rotation_matrix, glm::radians(yrot), glm::vec3(0.0f,1.0f,0.0f));
rotation_matrix = glm::rotate(rotation_matrix, glm::radians(zrot), glm::vec3(0.0f,0.0f,1.0f));
model_matrix = rotation_matrix;
//Creating the lookat and the up vectors for the camera
c_rotation_matrix = glm::rotate(glm::mat4(1.0f), glm::radians(c_xrot), glm::vec3(1.0f,0.0f,0.0f));
c_rotation_matrix = glm::rotate(c_rotation_matrix, glm::radians(c_yrot), glm::vec3(0.0f,1.0f,0.0f));
c_rotation_matrix = glm::rotate(c_rotation_matrix, glm::radians(c_zrot), glm::vec3(0.0f,0.0f,1.0f));
glm::vec4 c_pos = glm::vec4(c_xpos,c_ypos,c_zpos, 1.0)*c_rotation_matrix;
glm::vec4 c_up = glm::vec4(c_up_x,c_up_y,c_up_z, 1.0)*c_rotation_matrix;
//Creating the lookat matrix
lookat_matrix = glm::lookAt(glm::vec3(c_pos),glm::vec3(0.0),glm::vec3(c_up));
//creating the projection matrix
projection_matrix = glm::frustum(-1.0, 1.0, -1.0, 1.0, 1.0, 5.0);
view_matrix = projection_matrix*lookat_matrix;
glUniformMatrix4fv(viewMatrix, 1, GL_FALSE, glm::value_ptr(view_matrix));
// Draw the sphere
modelview_matrix = view_matrix*model_matrix;
glUniformMatrix4fv(uModelViewMatrix, 1, GL_FALSE, glm::value_ptr(modelview_matrix));
normal_matrix = glm::transpose (glm::inverse(glm::mat3(modelview_matrix)));
glUniformMatrix3fv(normalMatrix, 1, GL_FALSE, glm::value_ptr(normal_matrix));
// glBindTexture(GL_TEXTURE_2D, tex);
glBindVertexArray (vao[0]);
glDrawArrays(GL_TRIANGLES, 0, num_vertices);
}
int main(int argc, char** argv)
{
//! The pointer to the GLFW window
GLFWwindow* window;
//! Setting up the GLFW Error callback
glfwSetErrorCallback(csX75::error_callback);
//! Initialize GLFW
if (!glfwInit())
return -1;
//We want OpenGL 4.0
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
//This is for MacOSX - can be omitted otherwise
glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE);
//We don't want the old OpenGL
glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
//! Create a windowed mode window and its OpenGL context
window = glfwCreateWindow(512, 512, "CS475/CS675 Tutorial 6: Texturing a cube", NULL, NULL);
if (!window)
{
glfwTerminate();
return -1;
}
//! Make the window's context current
glfwMakeContextCurrent(window);
//Initialize GLEW
//Turn this on to get Shader based OpenGL
glewExperimental = GL_TRUE;
GLenum err = glewInit();
if (GLEW_OK != err)
{
//Problem: glewInit failed, something is seriously wrong.
std::cerr<<"GLEW Init Failed : %s"<<std::endl;
}
//Keyboard Callback
glfwSetKeyCallback(window, csX75::key_callback);
//Framebuffer resize callback
glfwSetFramebufferSizeCallback(window, csX75::framebuffer_size_callback);
// Ensure we can capture the escape key being pressed below
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
//Initialize GL state
csX75::initGL();
initBuffersGL();
// Loop until the user closes the window
while (glfwWindowShouldClose(window) == 0)
{
// Render here
renderGL();
// Swap front and back buffers
glfwSwapBuffers(window);
// Poll for and process events
glfwPollEvents();
}
glfwTerminate();
return 0;
}
我想要更改它以在不同的侧面上呈现不同的图像。
答案 0 :(得分：1)
如果要使用2个完全不同的纹理，请在片段着色器中将纹理绑定到2个不同的纹理单元。可以通过glActiveTexture设置纹理单位：
GLuint tex=LoadTexture("images/all1.bmp",256,256);
GLuint tex2=LoadTexture("images/another.bmp",256,256);
int unit_tex0 = 0; // texture unit 0 and binding point 0
int unit_tex1 = 1; // texture unit 1 and binding point 1
glActiveTexture( GL_TEXTURE0 + unit_tex0 );
glBindTexture(GL_TEXTURE_2D, tex);
glActiveTexture( GL_TEXTURE0 + unit_tex1 );
glBindTexture(GL_TEXTURE_2D, tex2);
此外，您必须在片段着色器中声明2个纹理采样器。纹理采样器必须与纹理单元关联。从GLSL 4.2版开始，这可以通过指定binding points在片段着色器中完成：
#version 420
layout (binding = 0) uniform sampler2D u_texture0;
layout (binding = 1) uniform sampler2D u_texture1;
或者，您可以将纹理单元索引分配给glUniform1i统一的纹理采样器：
uniform sampler2D u_texture0;
uniform sampler2D u_texture1;
GLuint location_tex0 = glGetUniformLocation( shaderProgram, "u_texture0" );
GLuint location_tex1 = glGetUniformLocation( shaderProgram, "u_texture1" );
glUniform1i( location_tex0, unit_tex0 );
glUniform1i( location_tex1, unit_tex1 );
要区分多维数据集的边，可以使用内置的顶点着色器变量gl_VertexID。
在顶点着色器中创建类型为out的{{3}} int变量，并将顶点ID传递给片段着色器：
flat out int vertex_id;
void main()
{
.....
vertex_id = gl_VertexID;
.....
}
在片段着色器中，您可以通过与顶点坐标对应的id来确定要使用的纹理。请注意，您有36个坐标，前3个面的ID形式为0到17，其他ID形式为18到35：
flat in int vertex_id;
void main()
{
.....
if ( vertex_id < 18 )
fragColor = texture(u_texture0, vertUV);
else
fragColor = texture(u_texture1, vertUV);
.....
}