我写iphone至极一个简单的应用程序显示一个旋转的立方体。 我正在使用glDrawElements(openGl es)绘制立方体的三角形并旋转它。我注意到,当我增加立方体100 * 100 * 100大小的体素的显示性能得到坏 (澄清:我不画整个多维数据集,我只画出它的轮廓(目)我得到的所有三角形通过在立方体上应用行进立方体算法......最终我得到类似于120k三角形的东西来绘制哪些由40k顶点表示)...使用顶点缓冲对象(VBO)在OpenGL ES(iPhone),以提高性能
要绘制立方体我拥有一个顶点数组,颜色和数组,如果索引指向顶点。 indices数组定义了要绘制的顶点的三角形。它作为参数传递给glDrawElements。
最近我一直红约了不同的技术来绘制使用顶点缓冲对象(VBO)的立方体。我实现了,但性能甚至沃瑟然后由以前的技术
这里是我的代码,也许我已经做了愚蠢的错误,任何改进的建议将好评:)
的方式,我用下面的文章作为参考:
http://playcontrol.net/ewing/jibberjabber/opengl_vertex_buffer_object.html http://iphonedevelopment.blogspot.com/2009/05/opengl-es-from-ground-up-table-of.html
//all the 7 variables down are initialized by other function at the beginning
GLushort* meshIndices; //array of indices (ushort)
MeshVertex* meshVertices; //array of vertices (floats)
Color3D* meshColors; //array of colors (floats)
int numberOfTriangles; //number of Triangle to draw the cube
int numberOfVertices; //number of all Vertices to draw the cube
int numberOfIndices; //number of all Indices to draw the cube, each 3 indices define 3 vertices which define 1 triangle
int numberOfColors; //number of colors used to draw the cube. each color is of tip Color3D
//in this function i initializing the VBOs
- (void) setupMeshVBOs {
glGenBuffers(1, &triangleVBO);
glBindBuffer(GL_ARRAY_BUFFER, triangleVBO);
const GLsizeiptr vertex_size = numberOfVertices * sizeof(MeshVertex);
const GLsizeiptr color_size = numberOfColors * sizeof(Color3D);
glBufferData(GL_ARRAY_BUFFER, vertex_size + color_size, 0, GL_STATIC_DRAW);
GLvoid* vbo_buffer = glMapBufferOES(GL_ARRAY_BUFFER, GL_WRITE_ONLY_OES);
memcpy(vbo_buffer, meshVertices, vertex_size);
GLbyte* temp = (GLbyte*)vbo_buffer;
temp += vertex_size;
memcpy((GLvoid*)temp, meshColors, color_size);
glUnmapBufferOES(GL_ARRAY_BUFFER);
glVertexPointer(3, GL_FLOAT, 0, (GLvoid*)((char*)NULL));
glColorPointer(4, GL_FLOAT, 0, (GLvoid*)((char*)NULL+vertex_size));
glGenBuffers(1, &triangleIBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, triangleIBO);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, numberOfIndices * sizeof(GLushort), meshIndices, GL_STATIC_DRAW);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
}
//this function is the one which draws the VBOs
- (void)drawView:(GLView*)view;
{
static GLfloat rot = 0.0;
glLoadIdentity();
glTranslatef(-1.0f,-2.0f,-20.0f);
glRotatef(rot,1.0f,1.0f,1.0f);
glClearColor(0.7, 0.7, 0.7, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glBindBuffer(GL_ARRAY_BUFFER, triangleVBO);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, triangleIBO);
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glDrawElements(GL_TRIANGLE_STRIP, numberOfIndices, GL_UNSIGNED_SHORT, (GLvoid*)((char*)NULL));
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_COLOR_ARRAY);
static NSTimeInterval lastDrawTime;
if (lastDrawTime)
{
NSTimeInterval timeSinceLastDraw = [NSDate timeIntervalSinceReferenceDate] - lastDrawTime;
rot+=50 * timeSinceLastDraw;
}
lastDrawTime = [NSDate timeIntervalSinceReferenceDate];
}
首先,你说在100^3体素的性能变得不好。这根本不算意外,因为那将是100万个体素。我假设每个体素是一个立方体,由12个三角形组成。每个渲染调用将会有1200万个三角形。这是*很多*。还要注意,当顶点和颜色数据交错时,VBOs *可能会更有效率。然而,至于iPhone(PowerVR),我不知道是否是这种情况。 – Arne
是的,我没有解释我的自我好,我已经编辑了相应的问题。立方体是100 * 100 * 100,但我不画整个立方体,我只绘制它的轮廓(网格)。通过在立方体上应用行军立方体算法,我得到了网格的所有三角形...最终,我得到了一个像120k三角形的图形,绘制了由40k顶点表示的图形... – alexpov