VBO fps problem can i draw 500 600 millions triangles ? if yes how please help me

OpenGL OpenGL: Basic Coding
1

hello

i am beginner. i have a problem with fps i am trying to see my GPU max performans with using VBO. i searched all day but i didnt fix this problem. i saw that everybody says GPU can draw 1 billion triangles(so 3 billion vertices) with VBO easily is it right? if it is right why i am taking 37 fps at only 8 million triangles(24million vertices) can you help me please sorry for bad english :).

i am not using shader also i dont know use it.
My GPU is (amd radeon hd 6870)
when 20k triangles fps=6000
when 8million triangles fps=37 and cpu usage %1 i think cpu don’t make bottleneck

my code like this:

i create in header file GLuint terrainVBO;

i made in init() fonk


glGenBuffers(1,&terrainVBO);
glBindBuffer(GL_ARRAY_BUFFER,terrainVBO);
glBufferData(GL_ARRAY_BUFFER,terrainVertices.size()*sizeof(terrainVec),&terrainVertices[0],GL_STATIC_DRAW);

and draw in my main loop:


glBindBuffer(GL_ARRAY_BUFFER,terrainVBO);
glEnableClientState(GL_VERTEX_ARRAY);
glVertexPointer(3,GL_FLOAT,3*sizeof(float),0);

glDrawArrays(GL_TRIANGLES,0,terrainVertices.size());

glDisableClientState(GL_VERTEX_ARRAY);
glBindBuffer(GL_ARRAY_BUFFER,0);

Summary : Can i draw 500 600 millions triangles (1.500.000.000 vertices) with good fps ? and how ? i could only draw 8 million triangles :frowning: please help me guys

2

The number of triangles is not that important. The size of your triangles matters far more. My crappy laptop can draw many millions of triangles if each triangle is only a single pixel in size if not less. But if each triangle is as large as the framebuffer I am capped at a few hundred thousands. There is no sense in counting triangles. Performance limits depend on many factors and is are a very complicated question on modern hardware.

3

Is (8 millions triangles =24.000.000 vertices for me i didnt draw normals,colors or textures so 24millions vertices * 3 (x,y,z) * sizeof(float)=288000000byte = 288megabyte ) size of triangles meaning ? if it is why my fps is falling to 37 at 288 megabyte also I’m grateful for your reply :slight_smile:

4

Not that size, the size of them on the screen.

5

is it grid size for terrain ? if it i tried to change grid size but i got same fps

6

No, the size in pixels.
If, when displayed, your triangle ends to a single pixel, it will render more fast that if it covers 1000 pixels, which will be more fast than if it covers 1000000 pixels.

7

Big triangle:

glBegin (GL_TRIANGLES);
glVertex (0,0,0);
glVertex (100,100,0);
glVertex (200,0,0);
glEnd ();

Small triangle:

glBegin (GL_TRIANGLES);
glVertex (0,0,0);
glVertex (1,1,0);
glVertex (2,0,0);
glEnd ();

The big triangle will be slower to draw than the small one. Vertex count is not the only factor that affects performance.

8

[QUOTE=mhagain;1287907]Big triangle:

glBegin (GL_TRIANGLES);
glVertex (0,0,0);
glVertex (100,100,0);
glVertex (200,0,0);
glEnd ();

Small triangle:

glBegin (GL_TRIANGLES);
glVertex (0,0,0);
glVertex (1,1,0);
glVertex (2,0,0);
glEnd ();

The big triangle will be slower to draw than the small one. Vertex count is not the only factor that affects performance.[/QUOTE]

i tested this with VBO (like my first message) but fps didnt change maybe it affects only glBegin glEnd ? sorry for delay, i saw your message after 3 days :slight_smile:

9

Did you test it with 1 triangle or with 100000 triangles?

10

with 1000*1000=1.000.000 triangles. i gave them 1 size and after i gave them 250 and 500 size but fps didnt change i will show with video can you watch . When i give 1 size i can go to end of terrain in 3 4 seconds you can see in video and if i give 250 or 500 size It takes much longer to go to the end of the terrain. Therefore i setup size of triangles correct why fps didnt change. Note: when video recorder off GPU using %100 and CPU doesnt do bottleneck and character doesnt affect fps when i close him still fps same

11

in case you want to measure (in nanoseconds) how long it takes to draw your stuff:
https://www.khronos.org/opengl/wiki/Query_Object#Timer_queries

here’s an example code:

Can i draw 500 600 millions triangles (1.500.000.000 vertices) with good fps ?

it depends on your graphics card, how you “shade” your triangles, how big they are, but certainly not with the “fixed-function pipeline” that you’re using.