OpenGl + SDL not working inside thread? (solved)

theHobbit · Post by **theHobbit** » Fri Sep 14, 2007 7:34 am

Hello.

I'm trying to use SDL + OpenGL and do the drawing stuff inside a thread. But the app crashes whenever I call some OpenGL routine inside a thread. However it works fine if it's done in the main func. Like this:

Code: Select all

#include <stdio.h>
#include <stdlib.h>

#include <SDL/SDL.h>
#include <GL/gl.h>
#include <GL/glu.h>

int width = 480;
int height = 272;

int main&#40; int argc, char *argv&#91;&#93; &#41;
&#123;    
    SDL_Init &#40;SDL_INIT_VIDEO&#41;;
    
    if &#40;!SDL_SetVideoMode&#40; width, height, 32, SDL_OPENGL &#41;&#41; &#123;
        fprintf &#40;stdout, "Failed to create window\n"&#41;;
        SDL_Quit&#40; &#41;;
        return 0;
    &#125;
    
    glViewport&#40; 0, 0, width, height &#41;;
    glMatrixMode&#40;GL_PROJECTION&#41;;
    glLoadIdentity&#40;&#41;;
    gluPerspective&#40;45, width/height, 1, 10&#41;;
    glMatrixMode&#40;GL_MODELVIEW&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;
	
	static int rotation = 0;
    float bheight;

    bheight = 3.0f;
    
    glLoadIdentity&#40;&#41;;
    gluLookAt&#40;0, 0, 5, 0, 0, 0, 0, 1, 0&#41;; 

    // Clear buffer
    glClearColor&#40;0.0f, 0.0f, 0.0f, 0.0f&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;

    glColor3f&#40;1.0f, 0.0f, 0.0f&#41;;

    // Spin round a bit
    glRotatef&#40;rotation++, 0, 0, 1&#41;;

    // Draw bar
    glBegin&#40;GL_POLYGON&#41;;
    glVertex3f&#40;-0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, bheight, 0&#41;;
    glVertex3f&#40;-0.1, bheight, 0&#41;;
    glEnd&#40;&#41;;

    glFinish&#40;&#41;;

    SDL_GL_SwapBuffers&#40;&#41;;
    
    SDL_Delay&#40; 5000 &#41;;
    SDL_Quit&#40; &#41;;
    return 0;
&#125;

But for some reason the app crashes when I try to do the rendering inside a thread like this:

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#include <stdio.h>
#include <stdlib.h>

#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>
#include <GL/gl.h>
#include <GL/glu.h>

SDL_Thread *thread = NULL;

int width = 480;
int height = 272;

int func&#40; void *data &#41;
&#123;              
    while &#40;1&#41; &#123;
    static int rotation = 0;
    float bheight;

    bheight = 3.0f;
    
    glLoadIdentity&#40;&#41;;
    gluLookAt&#40;0, 0, 5, 0, 0, 0, 0, 1, 0&#41;; 

    // Clear buffer
    glClearColor&#40;0.0f, 0.0f, 0.0f, 0.0f&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;

    glColor3f&#40;1.0f, 0.0f, 0.0f&#41;;

    // Spin round a bit
    glRotatef&#40;rotation++, 0, 0, 1&#41;;

    // Draw bar
    glBegin&#40;GL_POLYGON&#41;;
    glVertex3f&#40;-0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, bheight, 0&#41;;
    glVertex3f&#40;-0.1, bheight, 0&#41;;
    glEnd&#40;&#41;;

    glFinish&#40;&#41;;

    SDL_GL_SwapBuffers&#40;&#41;;

    SDL_Delay&#40;1000 / 70&#41;;
  &#125;
&#125;

int main&#40; int argc, char *argv&#91;&#93; &#41;
&#123;    
    SDL_Init &#40;SDL_INIT_VIDEO&#41;;
    
    if &#40;!SDL_SetVideoMode&#40; width, height, 32, SDL_OPENGL &#41;&#41; &#123;
        fprintf &#40;stdout, "Failed to create window\n"&#41;;
        SDL_Quit&#40; &#41;;
        return 0;
    &#125;
    
    glViewport&#40; 0, 0, width, height &#41;;
    glMatrixMode&#40;GL_PROJECTION&#41;;
    glLoadIdentity&#40;&#41;;
    gluPerspective&#40;45, width/height, 1, 10&#41;;
    glMatrixMode&#40;GL_MODELVIEW&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;

    thread = SDL_CreateThread&#40; func, NULL &#41;;     
	    
    SDL_Delay&#40; 5000 &#41;;
    SDL_Quit&#40; &#41;;
    return 0;
&#125;

I need this inside a thread because I'm working on something like a visualizer interface. Is there anyway to solve this? Hope anyone can help.
Sayounara

saulotmalo2 · Post by **saulotmalo2** » Fri Sep 14, 2007 7:43 am

i'm not sure about this but try using this while(1) on the main thread... is weird but it is for ensure that the thread creates well (also i have noticed that you're using SDL_Delay but it is only for try.

Code: Select all

#include <stdio.h>
#include <stdlib.h>

#include <SDL/SDL.h>
#include <SDL/SDL_thread.h>
#include <GL/gl.h>
#include <GL/glu.h>

SDL_Thread *thread = NULL;

int width = 480;
int height = 272;

int func&#40; void *data &#41;
&#123;             
    while &#40;1&#41; &#123;
    static int rotation = 0;
    float bheight;

    bheight = 3.0f;
   
    glLoadIdentity&#40;&#41;;
    gluLookAt&#40;0, 0, 5, 0, 0, 0, 0, 1, 0&#41;;

    // Clear buffer
    glClearColor&#40;0.0f, 0.0f, 0.0f, 0.0f&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;

    glColor3f&#40;1.0f, 0.0f, 0.0f&#41;;

    // Spin round a bit
    glRotatef&#40;rotation++, 0, 0, 1&#41;;

    // Draw bar
    glBegin&#40;GL_POLYGON&#41;;
    glVertex3f&#40;-0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, -1, 0&#41;;
    glVertex3f&#40;0.1, bheight, 0&#41;;
    glVertex3f&#40;-0.1, bheight, 0&#41;;
    glEnd&#40;&#41;;

    glFinish&#40;&#41;;

    SDL_GL_SwapBuffers&#40;&#41;;

    SDL_Delay&#40;1000 / 70&#41;;
  &#125;
&#125;

int main&#40; int argc, char *argv&#91;&#93; &#41;
&#123;   
    SDL_Init &#40;SDL_INIT_VIDEO&#41;;
   
    if &#40;!SDL_SetVideoMode&#40; width, height, 32, SDL_OPENGL &#41;&#41; &#123;
        fprintf &#40;stdout, "Failed to create window\n"&#41;;
        SDL_Quit&#40; &#41;;
        return 0;
    &#125;
   
    glViewport&#40; 0, 0, width, height &#41;;
    glMatrixMode&#40;GL_PROJECTION&#41;;
    glLoadIdentity&#40;&#41;;
    gluPerspective&#40;45, width/height, 1, 10&#41;;
    glMatrixMode&#40;GL_MODELVIEW&#41;;
    glClear&#40;GL_COLOR_BUFFER_BIT&#41;;

    thread = SDL_CreateThread&#40; func, NULL &#41;;     
    while&#40;1&#41;&#123; &#125;  
    SDL_Delay&#40; 5000 &#41;;
    SDL_Quit&#40; &#41;;
    return 0;
&#125;

Jim · Post by **Jim** » Fri Sep 14, 2007 8:13 am

This bit

Code: Select all

    while&#40;1&#41;&#123; &#125;

in your main loop is going to suck up all the CPU time. You need to put a sleep in there.

Jim

saulotmalo2 · Post by **saulotmalo2** » Fri Sep 14, 2007 9:16 am

yes, it slows down a lot the CPU but i tell him to try in order of testing if the problem was that the thread creation cost is to high not for ever. also as i've said before he is already using a SDL_Delay but i'm not sure of this working good.

theHobbit · Post by **theHobbit** » Fri Sep 14, 2007 9:50 am

Thanks tryied it but with the same results. Maybe OpenGL isn't thread safe?

saulotmalo2 · Post by **saulotmalo2** » Fri Sep 14, 2007 10:00 am

another question may be... are you sure the code inside is executing? i mean have you tried to put a cout or printf in order of knowing if it is running well? It sounds weird but when something doesn't work most times is a very simple thing other times can be because big problems ;)

theHobbit · Post by **theHobbit** » Fri Sep 14, 2007 10:12 am

Thanks for the fast reply. Yep I put

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    fprintf&#40; stdout, "Inside Thread" &#41;;

just before the

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glLoadIdentity&#40;&#41;;
    gluLookAt&#40;0, 0, 5, 0, 0, 0, 0, 1, 0&#41;;

routines and yes the stdout.txt file says a lot of 'Inside Thread' strings :)

J.F. · Post by **J.F.** » Fri Sep 14, 2007 4:13 pm

A quick check of the SDL code shows that SDL_CreateThread() doesn't create a thread with the PSP_THREAD_ATTR_VFPU attribute set, so any use of the VFPU will crash the PSP. I do believe PSPGL is rife with VFPU usage.

theHobbit · Post by **theHobbit** » Sat Sep 15, 2007 2:30 am

Thanks a lot J.F. I have changed this line in the SDL_systhread.c file:

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thread->handle = sceKernelCreateThread&#40;"SDL thread", ThreadEntry, 
					       priority, 0x8000, 0, NULL&#41;;

with this:

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thread->handle = sceKernelCreateThread&#40;"SDL thread", ThreadEntry, 
					       priority, 0x8000, PSP_THREAD_ATTR_VFPU, NULL&#41;;

Rebuilt SDL, and is working now : ). Well hope that doesn't break something else...

Thanks Everyone!!

jimparis · Post by **jimparis** » Tue Sep 18, 2007 3:03 am

Committed in rev. 2315