vertex-array | 易学教程

Using glBindVertexArray in update loop in DSA code or not

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问题 I'm the process of converting some opengl code to DSA and everywhere its written not to bind the vertex array, because its inherit in DSA. So I use GLuint VBO, VAO, indexBuffer; glCreateVertexArrays(1, &VAO); glCreateBuffers(1, &indexBuffer); glCreateBuffers(1, &VBO); ... instead of the glGen... counterparts. But now I just wonder whether there is a DSA version of binding the vertex arrays in the update loop. Now I have while (!glfwWindowShouldClose(window)) { glfwPollEvents(); glClearColor(0

How does OpenGL know what type each vertex buffer object is?

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问题 I've just read through a tutorial about Vertex Array Objects and Vertex Buffer Objects, and I can't work out from the following code how OpenGL knows the first VBO ( vertexBufferObjID[0] ) represents vertex coordinates, and the second VBO ( vertexBufferObjID[1] ) represents colour data? glGenBuffers(2, vertexBufferObjID); // VBO for vertex data glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObjID[0]); glBufferData(GL_ARRAY_BUFFER, 9*sizeof(GLfloat), vertices, GL_STATIC_DRAW); glVertexAttribPointer

Converting OpenGL draw lists to vertex arrays or VBOs

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问题 I'm trying to convert a program using draw lists, which are deprecated in OpenGL 3.0+, to use either vertex arrays or VBOs, but I'm not finding any examples of how to do the conversion. What's in the program now is this (happens to be Python, but really what I'm interested in is the appropriate OpenGL calls---it could just as well be C++, for example): dl = glGenLists(1) glNewList(dl, GL_COMPILE) glBindTexture(GL_TEXTURE_2D, texture) glBegin(GL_QUADS) glTexCoord2f(0, 0) glVertex2f(0, 0)

Converting OpenGL draw lists to vertex arrays or VBOs

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I'm trying to convert a program using draw lists, which are deprecated in OpenGL 3.0+, to use either vertex arrays or VBOs, but I'm not finding any examples of how to do the conversion. What's in the program now is this (happens to be Python, but really what I'm interested in is the appropriate OpenGL calls---it could just as well be C++, for example): dl = glGenLists(1) glNewList(dl, GL_COMPILE) glBindTexture(GL_TEXTURE_2D, texture) glBegin(GL_QUADS) glTexCoord2f(0, 0) glVertex2f(0, 0) glTexCoord2f(0, 1) glVertex2f(0, height) glTexCoord2f(1, 1) glVertex2f(width, height) glTexCoord2f(1, 0)

NDK OpenGL undefined reference to glVertexPointer

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When compiling the following C code with ndk-build in Terminal (I'm running Ubuntu): #include <jni.h> #include <GLES/gl.h> #include <GLES/glext.h> #include "org_opengldrawinjni_DrawinJNI.h" JNIEXPORT void JNICALL Java_org_opengldrawinjni_DrawinJNI_Draw (JNIEnv *envptr, jobject jobj) { GLfloat vertices[] = { 1.0, 0.0, 0.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0 }; GLubyte indices[] = { 0, 1, 2 }; glVertexPointer(3, GL_FLOAT, 0, vertices); glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_BYTE, indices); } with this Android.mk file: LOCAL_PATH := $(call my-dir) include $(CLEAR_VARS) LOCAL_MODULE := OpenGLJNI

Why does OpenGL's glDrawArrays() fail with GL_INVALID_OPERATION under Core Profile 3.2, but not 3.3 or 4.2?

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I have OpenGL rendering code calling glDrawArrays that works flawlessly when the OpenGL context is (automatically / implicitly obtained) 4.2 but fails consistently (GL_INVALID_OPERATION) with an explicitly requested OpenGL core context 3.2. (Shaders are always set to #version 150 in both cases but that's beside the point here I suspect.) According to specs, there are only two instances when glDrawArrays() fails with GL_INVALID_OPERATION: "if a non-zero buffer object name is bound to an enabled array and the buffer object's data store is currently mapped" -- I'm not doing any buffer mapping at

Hard time understanding indices with glDrawElements

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I'm trying to draw a terrain with GL_TRIANGLE_STRIP and glDrawElements but I'm having a really hard time understanding the indices thing behind glDrawElements ... Here's what I have so far: void Terrain::GenerateVertexBufferObjects(float ox, float oy, float oz) { float startWidth, startLength, *vArray; int vCount, vIndex = -1; // width = length = 256 startWidth = (width / 2.0f) - width; startLength = (length / 2.0f) - length; vCount = 3 * width * length; vArray = new float[vCount]; for(int z = 0; z < length; z++) { // vIndex == vIndex + width * 3 || width * 3 = 256 * 3 = 768 for(int x = 0; x <

OpenGL ES - How to Batch Render 500+ particles w/ different alphas, rotations, and scales?

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问题 I am developing an iOS game that will need to render 500-800 particles at a time. I have learned that it is a good idea to batch render many sprites in OpenGL ES instead of calling glDrawArrays(..) on every sprite in the game in order to be able to render more sprites w/out a drastic reduction in frame rate. My question is : how do I batch render 500+ particles that all have different alphas, rotations, and scales, but share the same texture atlas? The emphasis of this question is on the

OpenGL Vertex buffer object, can I access the vertex data for other uses such as collision detection?

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问题 I'm currently using the GLTools classes that come along with the Superbible 5th edition. I'm looking in the GLTriangleBatch class and it has the following code: // Create the master vertex array object glGenVertexArrays(1, &vertexArrayBufferObject); glBindVertexArray(vertexArrayBufferObject); // Create the buffer objects glGenBuffers(4, bufferObjects); #define VERTEX_DATA 0 #define NORMAL_DATA 1 #define TEXTURE_DATA 2 #define INDEX_DATA 3 // Copy data to video memory // Vertex data

Generating Smooth Normals from active Vertex Array

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I'm attempting to hack and modify several rendering features of an old opengl fixed pipeline game, by hooking into OpenGl calls, and my current mission is to implement shader lighting. I've already created an appropriate shader program that lights most of my objects correctly, but this game's terrain is drawn with no normal data provided. The game calls: void glVertexPointer(GLint size, GLenum type, GLsizei stride, const GLvoid * pointer); and void glDrawElements(GLenum mode, GLsizei count, GLenum type, const GLvoid * indices);` to define and draw the terrain, thus I have these functions both