PDA

View Full Version : VBO's much slower than VA's ??



finalbrainxp@t-online.de
05-25-2008, 02:35 PM
Hello,

I have a big world of ca. 2 Million Tiles (2D-Engine). For the graphics the tiles
uses subparts of Textures to avoid many Texture-Switchings.
To scroll in this big world I splitted the World in many "renderpages" with the size
of the screen. Each Renderpage knows, which Tiles belongs to them.
So If I scroll in my World, I have to draw max. 5000-6000 Tiles (Quads), instead
the whole 2 Million Tiles. Cause I have different Texture-Bindings and different Layers,
I developed my renderer with a few Vertex-Arrays (6 Layer and 8 different Textures per Layer = 48 VA's).

In the main-loop of my renderer I loop through the visible Renderpages and
store the Tiles-Koordinates in my VA's. Then I draw this VA's with glDrawArrays.
Because I use the VA's in the dynamic way, I get "only" 200 FPS with it.
So I decided to use VBO's with the VA's to get some more performance.
After I have modified the code, I got only 50 FPS!
Can somebody explain me, what I have done wrong and why is my renderer with VBO's
so much slower than my version only VA's ?

Here are parts of the Code with only the VA's and 200 FPS:



INITIALISATION:

...
...

this->numberOfLayers = 6;
this->numberOfStoragesPerLayer = 4;
this->vertexArray = new VertexArray*[this->numberOfLayers];

for (int l=0; l < this->numberOfLayers; l++)
{
this->vertexArray[l] = new VertexArray[this->numberOfStoragesPerLayer];

for (int z=0; z < this->numberOfStoragesPerLayer; z++)
{
this->vertexArray[l][z].setSizeOfVertexArray(5000 * 12);
this->vertexArray[l][z].setSizeOfColorArray(5000 *16);
this->vertexArray[l][z].setSizeOfTexCoordArray(5000 *8);
}
}
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

...
...

MAINLOOP:

...
...
for (int i=0; i < 4;i++)
{
if (screenX[i] == -1 || screenY[i] == -1)
continue;

vector<Tile> * tiles = this->renderPages[screenX[i]][screenY[i]].getTiles();

for (vector<Tile>::iterator tilesIter=tiles->begin(); tilesIter < tiles->end(); tilesIter++)
{
float layer = tilesIter->layer;
float x = tilesIter->x -(*camX);
float y = tilesIter->y -(*camY);
float width = tilesIter->width;
float height = tilesIter->height;


float rectAX1 = x;
float rectAX2 = x+width;
float rectAY1 = y;
float rectAY2 = y+height;
float rectBX1 = 0.0f;
float rectBX2 = this->screenWidth;
float rectBY1 = 0.0f;
float rectBY2 = this->screenHeight;

if (!(rectAX2 >= rectBX1 &amp;&amp;
rectAX1 <= rectBX2 &amp;&amp;
rectAY2 >= rectBY1 &amp;&amp;
rectAY1 <= rectBY2))
continue;

float colorRed = tilesIter->rgbaColor.red;
float colorGreen = tilesIter->rgbaColor.green;
float colorBlue = tilesIter->rgbaColor.blue;
float colorAlpha = tilesIter->rgbaColor.alpha;
float texLeft = tilesIter->texLeft;
float texTop = tilesIter->texTop;
float texRight = tilesIter->texRight;
float texBottom = tilesIter->texBottom;
int storage = tilesIter->storagePos;

int v = this->vertexArray[(int)layer][storage].v;
int c = this->vertexArray[(int)layer][storage].c;
int t = this->vertexArray[(int)layer][storage].t;
this->vertexArray[(int)layer][storage].vertices[v] = x;
this->vertexArray[(int)layer][storage].vertices[v+1] = y;
this->vertexArray[(int)layer][storage].vertices[v+2] = -layer;

this->vertexArray[(int)layer][storage].vertices[v+3] = x;
this->vertexArray[(int)layer][storage].vertices[v+4] = y + height;
this->vertexArray[(int)layer][storage].vertices[v+5] = -layer;

this->vertexArray[(int)layer][storage].vertices[v+6] = x + width;
this->vertexArray[(int)layer][storage].vertices[v+7] = y + height;
this->vertexArray[(int)layer][storage].vertices[v+8] = -layer;

this->vertexArray[(int)layer][storage].vertices[v+9] = x + width;
this->vertexArray[(int)layer][storage].vertices[v+10] = y;
this->vertexArray[(int)layer][storage].vertices[v+11] = -layer;

this->vertexArray[(int)layer][storage].colors[c] = colorRed;
this->vertexArray[(int)layer][storage].colors[c+1] = colorGreen;
this->vertexArray[(int)layer][storage].colors[c+2] = colorBlue;
this->vertexArray[(int)layer][storage].colors[c+3] = colorAlpha;

this->vertexArray[(int)layer][storage].colors[c+4] = colorRed;
this->vertexArray[(int)layer][storage].colors[c+5] = colorGreen;
this->vertexArray[(int)layer][storage].colors[c+6] = colorBlue;
this->vertexArray[(int)layer][storage].colors[c+7] = colorAlpha;

this->vertexArray[(int)layer][storage].colors[c+8] = colorRed;
this->vertexArray[(int)layer][storage].colors[c+9] = colorGreen;
this->vertexArray[(int)layer][storage].colors[c+10] = colorBlue;
this->vertexArray[(int)layer][storage].colors[c+11] = colorAlpha;

this->vertexArray[(int)layer][storage].colors[c+12] = colorRed;
this->vertexArray[(int)layer][storage].colors[c+13] = colorGreen;
this->vertexArray[(int)layer][storage].colors[c+14] = colorBlue;
this->vertexArray[(int)layer][storage].colors[c+15] = colorAlpha;

this->vertexArray[(int)layer][storage].texCoords[t] = texLeft;
this->vertexArray[(int)layer][storage].texCoords[t+1] = texTop;

this->vertexArray[(int)layer][storage].texCoords[t+2] = texLeft;
this->vertexArray[(int)layer][storage].texCoords[t+3] = texBottom;

this->vertexArray[(int)layer][storage].texCoords[t+4] = texRight;
this->vertexArray[(int)layer][storage].texCoords[t+5] = texBottom;

this->vertexArray[(int)layer][storage].texCoords[t+6] = texRight;
this->vertexArray[(int)layer][storage].texCoords[t+7] = texTop;

this->vertexArray[(int)layer][storage].v += 12;
this->vertexArray[(int)layer][storage].c += 16;
this->vertexArray[(int)layer][storage].t += 8;
}
}


for (int l = this->numberOfLayers-1; l >= 0; l--)
{
for (int i = 0; i < this->numberOfStoragesPerLayer; i++)
{
if (this->vertexArray[l][i].v == 0)
continue;

glVertexPointer(3,GL_FLOAT,0,this->vertexArray[l][i].vertices);
glColorPointer(4,GL_FLOAT,0,this->vertexArray[l][i].colors);
glTexCoordPointer(2,GL_FLOAT,0,this->vertexArray[l][i].texCoords);

glDrawArrays(GL_QUADS,0, (this->vertexArray[l][i].v / 3));
}
}

...
...




And here is the slow VBO Version with only 50 FPS:




INITIALISATION:

...
...

GLenum glewOK = glewInit();

if (glewOK != GLEW_OK)
return;


this->numberOfLayers = 6;
this->numberOfStoragesPerLayer = 8;
this->numberOfMaxQuadPerStorage = 1000;

glGenBuffers(1, this->vertexBuffer);
glBindBuffer(GL_ARRAY_BUFFER, this->vertexBuffer[0]);

this->bufferSize = ((this->numberOfMaxQuadPerStorage * sizeof(float) * 36) *
this->numberOfStoragesPerLayer *
this->numberOfLayers);
glBufferData(GL_ARRAY_BUFFER, this->bufferSize, NULL, GL_DYNAMIC_DRAW);

vertexIndexer = new int*[this->numberOfLayers];

for (int l=0; l < this->numberOfLayers; l++)
{
vertexIndexer[l] = new int[this->numberOfStoragesPerLayer];
memset(vertexIndexer[l],0, this->numberOfStoragesPerLayer * sizeof(int));
}

glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);

...
...



MAINLOOP:

...
...


for (int l=0; l < this->numberOfLayers; l++)
memset(vertexIndexer[l],0, this->numberOfStoragesPerLayer * sizeof(int));


float * bufferPtr;
bufferPtr = (float*)glMapBuffer(GL_ARRAY_BUFFER, GL_WRITE_ONLY);


for (int i=0; i < 4;i++)
{
if (screenX[i] == -1 || screenY[i] == -1)
continue;

vector<Tile> * tiles = this->renderPages[screenX[i]][screenY[i]].getTiles();

for (vector<Tile>::iterator tilesIter=tiles->begin(); tilesIter < tiles->end(); tilesIter++)
{
float layer = tilesIter->layer;
float x = tilesIter->x -(*camX);
float y = tilesIter->y -(*camY);
float width = tilesIter->width;
float height = tilesIter->height;

float rectAX1 = x;
float rectAX2 = x+width;
float rectAY1 = y;
float rectAY2 = y+height;
float rectBX1 = 0.0f;
float rectBX2 = this->screenWidth;
float rectBY1 = 0.0f;
float rectBY2 = this->screenHeight;

if (!(rectAX2 >= rectBX1 &amp;&amp;
rectAX1 <= rectBX2 &amp;&amp;
rectAY2 >= rectBY1 &amp;&amp;
rectAY1 <= rectBY2))
continue;

float colorRed = tilesIter->rgbaColor.red;
float colorGreen = tilesIter->rgbaColor.green;
float colorBlue = tilesIter->rgbaColor.blue;
float colorAlpha = tilesIter->rgbaColor.alpha;
float texLeft = tilesIter->texLeft;
float texTop = tilesIter->texTop;
float texRight = tilesIter->texRight;
float texBottom = tilesIter->texBottom;
int storage = tilesIter->storagePos;

int layerOffset = (int)layer * (this->numberOfMaxQuadPerStorage * 36 * this->numberOfStoragesPerLayer);
int storageOffset = layerOffset + (storage * this->numberOfMaxQuadPerStorage * 36);
int tileIndex = storageOffset + (vertexIndexer[(int)layer][storage] * 36);

//1 Vertice
bufferPtr[tileIndex] = x;
bufferPtr[tileIndex + 1] = y;
bufferPtr[tileIndex + 2] = -layer;
bufferPtr[tileIndex + 3] = colorRed;
bufferPtr[tileIndex + 4] = colorGreen;
bufferPtr[tileIndex + 5] = colorBlue;
bufferPtr[tileIndex + 6] = colorAlpha;
bufferPtr[tileIndex + 7] = texLeft;
bufferPtr[tileIndex + 8] = texTop;

//2 Vertice
bufferPtr[tileIndex + 9] = x;
bufferPtr[tileIndex + 10] = y + height;
bufferPtr[tileIndex + 11] = -layer;
bufferPtr[tileIndex + 12] = colorRed;
bufferPtr[tileIndex + 13] = colorGreen;
bufferPtr[tileIndex + 14] = colorBlue;
bufferPtr[tileIndex + 15] = colorAlpha;
bufferPtr[tileIndex + 16] = texLeft;
bufferPtr[tileIndex + 17] = texBottom;

//3 Vertice
bufferPtr[tileIndex + 18] = x + width;
bufferPtr[tileIndex + 19] = y + height;
bufferPtr[tileIndex + 20] = -layer;
bufferPtr[tileIndex + 21] = colorRed;
bufferPtr[tileIndex + 22] = colorGreen;
bufferPtr[tileIndex + 23] = colorBlue;
bufferPtr[tileIndex + 24] = colorAlpha;
bufferPtr[tileIndex + 25] = texRight;
bufferPtr[tileIndex + 26] = texBottom;

//4 Vertice
bufferPtr[tileIndex + 27] = x + width;
bufferPtr[tileIndex + 28] = y;
bufferPtr[tileIndex + 29] = -layer;
bufferPtr[tileIndex + 30] = colorRed;
bufferPtr[tileIndex + 31] = colorGreen;
bufferPtr[tileIndex + 32] = colorBlue;
bufferPtr[tileIndex + 33] = colorAlpha;
bufferPtr[tileIndex + 34] = texRight;
bufferPtr[tileIndex + 35] = texTop;
vertexIndexer[(int)layer][storage]++;

}
}

glUnmapBuffer(GL_ARRAY_BUFFER);

for (int l = this->numberOfLayers-1; l >= 0; l--)
{
for (int i = 0; i < this->numberOfStoragesPerLayer; i++)
{
if (vertexIndexer[l][i] == 0)
continue;

int layerOffset = l * (this->numberOfMaxQuadPerStorage * 36 * this->numberOfStoragesPerLayer *sizeof(float));
int storageOffset = layerOffset + (i * this->numberOfMaxQuadPerStorage * 36 * sizeof(float));

glVertexPointer(3,GL_FLOAT,9*sizeof(float),BUFFER_ OFFSET(storageOffset));
glColorPointer(4,GL_FLOAT,9*sizeof(float),BUFFER_O FFSET(storageOffset+3*sizeof(float)));
glTexCoordPointer(2,GL_FLOAT,9*sizeof(float),BUFFE R_OFFSET(storageOffset+7*sizeof(float)));
glDrawArrays(GL_QUADS,0, vertexIndexer[l][i]*4);
}
}

...
...




Can somebody see what I do wrong or where my bottleneck could be ?


Thanks and Greetz

fbrjogl

Lord crc
05-25-2008, 06:44 PM
I didn't look too closely, but if you overwrite the entire buffer using MapBuffer, you really should call BufferSubData() specifying the size of the entire buffer and passing NULL as the data pointer.

This way you signal that the old data isn't needed, so that the driver can optimize things.

Also, it's not like VBO's are the holy grail of issuing data to the GPU. In some cases VA's work better.

-NiCo-
05-26-2008, 12:12 AM
Putting the glVertexPointer call after the glColorPointer and glTexCoordPointer calls may also increase performance. I see you're always respecifying the buffers contents, isn't there a way to statically generate the vertex buffer data and select the data you need from those static buffers in the main loop?

finalbrainxp@t-online.de
05-26-2008, 09:26 AM
Hi Thanx for the answers. I cannot statically create a vertexbuffer, because my world has to many tiles :( So I load all
tiles static in the RAM (200 MB!), and then I select only portions of them, which I render with the VA's. Or is there a better way to
realize a 2D-Scrolling Platform Game ? I have tried many things out, but this version seems now my best solution. Before this I used a Tile-Engine, which was faster then 200FPS, but there I was not able to place the tiles with different sizes on any coordinate.
With this solution of renderpages I can handle this very dynamicly.
I will try out your solutions and will then post my new results.