我寫iphone至極一個簡單的應用程序顯示一個旋轉的立方體。 我正在使用glDrawElements(openGl es)繪製立方體的三角形並旋轉它。我注意到,當我增加立方體100 * 100 * 100大小的體素的顯示性能得到壞 (澄清:我不畫整個多維數據集,我只畫出它的輪廓(目)我得到的所有三角形通過在立方體上應用行進立方體算法......最終我得到類似於120k三角形的東西來繪製哪些由40k頂點表示)...使用頂點緩衝對象(VBO)在OpenGL ES(iPhone),以提高性能
要繪製立方體我擁有一個頂點數組,顏色和數組,如果索引指向頂點。 indices數組定義了要繪製的頂點的三角形。它作爲參數傳遞給glDrawElements。
最近我一直紅約了不同的技術來繪製使用頂點緩衝對象(VBO)的立方體。我實現了,但性能甚至沃瑟然後由以前的技術
這裏是我的代碼,也許我已經做了愚蠢的錯誤,任何改進的建議將好評:)
的方式,我用下面的文章作爲參考:
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,你說在100^3體素的性能變得不好。這根本不算意外,因爲那將是100萬個體素。我假設每個體素是一個立方體,由12個三角形組成。每個渲染調用將會有1200萬個三角形。這是*很多*。還要注意,當頂點和顏色數據交錯時,VBOs *可能會更有效率。然而,至於iPhone(PowerVR),我不知道是否是這種情況。 – Arne
是的,我沒有解釋我的自我好,我已經編輯了相應的問題。立方體是100 * 100 * 100,但我不畫整個立方體,我只繪製它的輪廓(網格)。通過在立方體上應用行軍立方體算法,我得到了網格的所有三角形...最終,我得到了一個像120k三角形的圖形,繪製了由40k頂點表示的圖形... – alexpov