GL's window space is defined so that integer coordinates represent the corners of the pixels, the pixel centers lie at half integer coordinates. While glReadPixels addresses a specific pixel with integer coordinates, the whole transformation math works with floating point and can represent arbitrary sub-pixel positions. So basically, you must query both sizes, and than can appropriately scale the mouse coords from screen coords to the actual pixels you need. GLFW generally provides two sizes for a window, glfwGetWindowSize will return the result in said virtual screen coordinates, while glfwGetFramebufferSize will return the actual size in pixels, relevant for OpenGL. The ratio between screen coordinates and pixels may alsoĬhange at run-time depending on which monitor the window is currently
#MOUSE COORDINATES MAC#
Won't on every other machine, for example on a Mac with a Retinaĭisplay. Pixels and screen coordinates may map 1:1 on your machine, but they GLFW uses the concept of "virtual screen coordinates" which don't necessarily map to pixels:
#MOUSE COORDINATES CODE#
Your code assumes that the coordinates you get back from GLFW are in pixels. (We will see later that that isn't exactly true either.)
Since ypos should be in, the correct formula is height-1 - ypos, so you are also off by one here.
While you flip to that convention for your win variable, you do still use the wrong origin for reading the depth buffer.įurthermore, your flipping is wrong.
glReadPixels is a GL function, and as such adheres to GL's conventions, with the origin beeing the lower left pixel. There are a couple of issues with this sequence: glfwGetCursorPos(window, &xpos, &ypos) So in order to convert screen to world coordinates I should use a transform matrix from one mesh, but what happens if a have many meshes and i want to convert from screen to world coordinates? what model matrix should I multuply by camera view matrix to form ModelView matrix? The second problem is, that as said in the glm docs ( ) the result is returned in object coordinates. If i use this values to translate the mesh, the mesh suffers a small translate and doesn't follow the mouse pointer. Now, I have 2 problem, the first is that the world vector that I get from glm::unProject has a very small x, y and z. Glm::vec3 world = glm::unProject(win, mesh.getView() * mesh.getTransform(),m_projection,viewport) Glm::vec4 viewport(0.0f,0.0f,(float)width, (float)height) GlReadPixels(xpos, ypos, 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &zpos) This is my code: static void mouse_callback(GLFWwindow* window, int button, int action, int mods) I am using glm for that purpose (also I am using glfw) I want to convert from Screen coordinates to world coordinates in OpenGL.
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