首先 - 代码：
std::vector<glm::vec3> verticescopy;
std::vector<glm::vec2> newUVs;
/*Generating new UV Coordinates*/
void keyfunction(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if (key == GLFW_KEY_R && action == GLFW_PRESS)
{
glm::vec3 coords2D;
GLdouble point2DX, point2DY, point2DZ;
GLdouble model_view[16];
glGetDoublev(GL_MODELVIEW_MATRIX, model_view);
GLdouble projection[16];
glGetDoublev(GL_PROJECTION_MATRIX, projection);
GLint viewport[4];
glGetIntegerv(GL_VIEWPORT, viewport);
for (int i = 0; i < verticescopy.size(); i++)
{
gluProject((double)verticescopy[i].x, (double)verticescopy[i].y, (double)verticescopy[i].z,
model_view, projection, viewport,
&point2DX, &point2DY, &point2DZ);
glm::vec2 UV;
UV.x = point2DX / 600;
UV.y = (point2DY - 800) / 800; /* I make Y - 800, because values from glProject are generated from (0,1), not (0,0) */
newUVs.push_back(UV);
}
}
}
int main(void)
{
if (!glfwInit())
{
fprintf(stderr, "Failed to initialize GLFW\n");
getchar();
return -1;
}
glfwWindowHint(GLFW_SAMPLES, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 2);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 1);
window = glfwCreateWindow(600, 800, "Window", NULL, NULL);
if (window == NULL)
{
fprintf(stderr, "Nie utworzono okna GLFW.\n");
getchar();
glfwTerminate();
return -1;
}
glfwMakeContextCurrent(window);
glewExperimental = true;
if (glewInit() != GLEW_OK)
{
fprintf(stderr, "Blad GLEW.\n");
getchar();
glfwTerminate();
return -1;
}
glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
glfwSetInputMode(window, GLFW_CURSOR, GLFW_CURSOR_DISABLED);
glfwPollEvents();
glfwSetCursorPos(window, 1024 / 2, 768 / 2);
glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
glEnable(GL_CULL_FACE);
GLuint VertexArrayID;
glGenVertexArrays(1, &VertexArrayID);
glBindVertexArray(VertexArrayID);
GLuint programID = LoadShaders("TransformVertexShader.vertexshader", "TextureFragmentShader.fragmentshader");
GLuint MatrixID = glGetUniformLocation(programID, "MVP");
GLuint Texture = loadBMP_custom("skull-xray.bmp");
GLuint TextureID = glGetUniformLocation(programID, "myTextureSampler");
std::vector<glm::vec3> vertices;
std::vector<glm::vec2> uvs;
std::vector<glm::vec3> normals;
bool res = loadOBJ("czaszkazeby.obj", vertices, uvs, normals);
for (int i = 0; i < vertices.size(); i++)
{
verticescopy.push_back(vertices[i]);
}
GLuint vertexbuffer;
glGenBuffers(1, &vertexbuffer);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glBufferData(GL_ARRAY_BUFFER, vertices.size() * sizeof(glm::vec3), &vertices[0], GL_STATIC_DRAW);
unsigned int Texture2DTextureID = loadBMP_custom("skull1.bmp");
unsigned int Texture2DVertexBufferID;
unsigned int Texture2DUVBufferID;
unsigned int Texture2DShaderID = LoadShaders("TextVertexShader.vertexshader", "TextVertexShader.fragmentshader");
unsigned int Texture2DUniformID = glGetUniformLocation(Texture2DShaderID, "myTextureSampler");
glGenBuffers(1, &Texture2DVertexBufferID);
glGenBuffers(1, &Texture2DUVBufferID);
glfwSetKeyCallback(window, keyfunction);
do{
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glUseProgram(programID);
computeMatricesFromInputs();
glm::mat4 ProjectionMatrix = getProjectionMatrix();
glm::mat4 ViewMatrix = getViewMatrix();
glm::mat4 ModelMatrix = glm::mat4(1.0);
glm::mat4 MVP = ProjectionMatrix * ViewMatrix * ModelMatrix;
glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
GLuint uvbuffer;
glGenBuffers(1, &uvbuffer);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glBufferData(GL_ARRAY_BUFFER, newUVs.size() * sizeof(glm::vec2), &newUVs[0], GL_DYNAMIC_DRAW);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, Texture);
glUniform1i(TextureID, 0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, uvbuffer);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
glDrawArrays(GL_TRIANGLES, 0, vertices.size());
/* HUD drawing, not really important for the problem (I know this is bad, but this is not the main problem) */
std::vector<glm::vec2> verticesTexture;
std::vector<glm::vec2> UVsTexture;
glm::vec2 vertex_up_left = glm::vec2(0, 600);
glm::vec2 vertex_up_right = glm::vec2(800, 600);
glm::vec2 vertex_down_right = glm::vec2(800, 0);
glm::vec2 vertex_down_left = glm::vec2(0, 0);
verticesTexture.push_back(vertex_up_left);
verticesTexture.push_back(vertex_down_left);
verticesTexture.push_back(vertex_up_right);
verticesTexture.push_back(vertex_down_right);
verticesTexture.push_back(vertex_up_right);
verticesTexture.push_back(vertex_down_left);
glm::vec2 uv_up_left = glm::vec2(0, 1);
glm::vec2 uv_up_right = glm::vec2(1, 1);
glm::vec2 uv_down_right = glm::vec2(1, 0);
glm::vec2 uv_down_left = glm::vec2(0, 0);
UVsTexture.push_back(uv_up_left);
UVsTexture.push_back(uv_down_left);
UVsTexture.push_back(uv_up_right);
UVsTexture.push_back(uv_down_right);
UVsTexture.push_back(uv_up_right);
UVsTexture.push_back(uv_down_left);
glBindBuffer(GL_ARRAY_BUFFER, Texture2DVertexBufferID);
glBufferData(GL_ARRAY_BUFFER, verticesTexture.size() * sizeof(glm::vec2), &verticesTexture[0], GL_STATIC_DRAW);
glBindBuffer(GL_ARRAY_BUFFER, Texture2DUVBufferID);
glBufferData(GL_ARRAY_BUFFER, UVsTexture.size() * sizeof(glm::vec2), &UVsTexture[0], GL_STATIC_DRAW);
glUseProgram(Texture2DShaderID);
glActiveTexture(GL_TEXTURE1);
glBindTexture(GL_TEXTURE_2D, Texture2DTextureID);
glUniform1i(Texture2DUniformID, 0);
glEnableVertexAttribArray(0);
glBindBuffer(GL_ARRAY_BUFFER, Texture2DVertexBufferID);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnableVertexAttribArray(1);
glBindBuffer(GL_ARRAY_BUFFER, Texture2DUVBufferID);
glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, 0, (void*)0);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glDrawArrays(GL_TRIANGLES, 0, verticesTexture.size());
/* End of HUD code */
glDisable(GL_BLEND);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glfwSwapBuffers(window);
glfwPollEvents();
}
while (glfwGetKey(window, GLFW_KEY_ESCAPE) != GLFW_PRESS &&
glfwWindowShouldClose(window) == 0);
glDeleteBuffers(1, &vertexbuffer);
glDeleteProgram(programID);
glDeleteTextures(1, &TextureID);
glDeleteVertexArrays(1, &VertexArrayID);
glfwTerminate();
return 0;
}
你可以认为这不是我正在寻找的效果。我想要的是将头骨X射线纹理（你可以在图像上看到）放在头骨模型的前面（就像人们为万圣节等画脸） 我使用gluProject将3D坐标转换为2D坐标（世界到屏幕）。当我获得点的二维坐标时，我只需将其除以纹理的宽度或高度（取决于坐标类型），这将获得此点的UV坐标。我的想法中是否有一些漏洞会导致这种奇怪的纹理变形？
答案 0 :(得分：4)
我使用gluProject将3D坐标转换为2D坐标（世界到屏幕）。当我获得点的二维坐标时，我只需将其除以纹理的宽度或高度（取决于坐标类型），这将获得此点的UV坐标。我的想法中是否有一些漏洞导致这种奇怪的纹理？
是。显然，您认为您的纹理坐标在某种程度上取决于模型的方向和投影方式。这意味着如果您移动“相机”，纹理坐标将不得不改变。这显然是错误的（显然，如果有人知道，纹理坐标应该如何工作）。顺便说一句，在OpenGL中，纹理坐标用S，T，R和Q表示，而不是UV。
纹理坐标将顶点与图像中的特定位置相关联。该图像空间位置可以完全独立于顶点在模型空间中的位置;程序纹理或反射图可能存在关系，但一般情况下它们是完全独立的。
通常不会生成纹理坐标，而是在创建3D模型时由艺术家手动定义，然后将其另存为模型数据。
我想要的是将头骨X射线纹理（可以在图像上看到）放在头骨模型的前面（就像人们为万圣节等画脸一样）。
假设你真的想要去纹理生成方法，那么这就是纹理空间到模型空间的平面投影。你必须知道你的头骨是哪个方向。为了写这个，头部的顶部是Y +，左边是X +，鼻子是Z +，那么你的X射线图像将投射到XY平面。让我们进一步假设您的X射线图像贴合裁剪。定义纹理空间以使图像适合范围] 0,1 [^ n（其中n是图像的维度）。这意味着无论顶点位置的X和Y分量的值范围是什么，都必须将其映射到范围] 0,1 [分别。
这给出了以下peudocode：
min_X = +inf
max_X = -inf
min_Y = +inf
max_Y = -inf
foreach vertex in model:
min_X = min(min_X, vertex.position.x)
min_Y = min(min_Y, vertex.position.y)
max_X = max(max_X, vertex.position.x)
max_Y = max(max_Y, vertex.position.y)
k_X = 1/(max_X - min_X)
k_Y = 1/(max_Y - min_Y)
foreach vertex in model:
vertex.texturecoordinate.s = (vertex.position.x - min_X) * k_X
vertex.texturecoordinate.t = (vertex.position.y - min_Y) * k_Y