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Fugitive

OpenGL OpenGL 3.2 and SDL 1.3

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Hi guys, I have been trying to run some simple OpenGL 3.2 tutorials with SDL 1.3, and have been running into some strange problems. My hunch is that its is a memory-leak, but could be something else. The problem, stripped down to its bare minimum is Tutorial 4 (from here: http://www.opengl.org/wiki/Tutorial4:_Using_Indices_and_Geometry_Shaders_(C_/SDL) ) I have only included a header file to initialize opengl extensions (since the original tutorial doesnt do that), and removed gl3.h in favour of gl.h, and glext.h. In addition, here is the init code:
if (initGLExtensions() == false)
	{
		sdldie("Unable to load openGL extensions");
	}
I am presented with a blank white screen. Here is the Visual Studio project: http://rapidshare.com/files/371298070/SDL_GL_test_2.zip (Its about 5-6 mb) The strange thing is, it compiles fine with Borland C++ Builder 2009 and 2010 (trial edition), but then causes memory leaks further down the line when I try to expand the code. Any ideas? Kind regards, Fugi

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Can you please be more descriptive what the problem is?

You said you got a white screen, is that not what you expect to see? Why do you think you have a leak? Is your program crashing?

It would probably help you to post some relevant code sections (in source tag) so we could look over it. I'd would normally be happy to review your code but I'm not going to go bother with rapidshare to look it over.

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The rapidshare link has a 'free user' download link, which allows you to download with only a 28 second wait. How about easyshare: http://www.easy-share.com/1909729478/SDL GL test 2.zip

In any event, the program is supposed to show some triangles, and a geometry shader that turns it into a closed 3d shape. Instead, the window remains blank until the loop is over, then the window closes without any error or warning.

What leads me to believe there is a memory leak is the compiled version on C++ builder. It compiles fine, however, simple things such as

char *test="test";
string x;
x=test; // <===commenting this line makes it show something again!


would cause the program to display a blank screen. No crash nothing. If i comment those lines out, viola, I see the model again. Or something like trying to append more than 2000 bytes would suddenly cause the program to go 'blank' again. Reducing the number of bytes (and recompiling) would show the model. At first I thought there was something weird with the STL string class, but then if I removed all strings, it would give me weird errors further down the line (in code that was working before) related to heap damage when I would try to free memory previously allocated.

To me, those things seem like standard memory-leaking symptoms...subtle, hard-to-track, and constantly moving. Whats worrying though, is that I have removed almost all of my own code, so the memory leak is either in the tutorial, or SDL!

Kind regards,
Fugi

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Some source: tutorialmain.cpp

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

#include "MyOpenGLExtensions.h"

/* Ensure we are using opengl's core profile only */
//#define GL3_PROTOTYPES 1
//#include <GL3/gl3.h>
#include <gl\gl.h>
#include<gl\glext.h>

#include <SDL\SDL.h>
#include <math.h>

#include "utils.h"

void setupwindow(SDL_WindowID *window, SDL_GLContext *context)
{
if (SDL_Init(SDL_INIT_VIDEO) < 0) /* Initialize SDL's Video subsystem */
sdldie("Unable to initialize SDL"); /* Or die on error */

/* Request an opengl 3.2 context.
* SDL doesn't have the ability to choose which profile at this time of writing,
* but it should default to the core profile */

SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);

/* Enable double buffering with a 24bit Z buffer.
* You may need to change this to 16 or 32 for your system */

SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
SDL_GL_SetAttribute(SDL_GL_DEPTH_SIZE, 24);

/* Enable multisampling for a nice antialiased effect */
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLEBUFFERS, 1);
SDL_GL_SetAttribute(SDL_GL_MULTISAMPLESAMPLES, 4);

/* Create our window centered at 512x512 resolution */
*window = SDL_CreateWindow("Tutorial 4", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
512, 512, SDL_WINDOW_OPENGL | SDL_WINDOW_SHOWN);
if (!*window) /* Die if creation failed */
sdldie("Unable to create window");

/* Create our opengl context and attach it to our window */
*context = SDL_GL_CreateContext(*window);


if (initGLExtensions() == false)
{
sdldie("Unable to load openGL extensions");
}


/* This makes our buffer swap syncronized with the monitor's vertical refresh */
SDL_GL_SetSwapInterval(1);

/* Enable Z depth testing so objects closest to the viewpoint are in front of objects further away */
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LESS);
}

void drawscene(SDL_WindowID window)
{
int i; /* Simple iterator */
GLuint vao, vbo[3]; /* Create handles for our Vertex Array Object and three Vertex Buffer Objects */
GLfloat projectionmatrix[16]; /* Our projection matrix starts with all 0s */
GLfloat modelmatrix[16]; /* Our model matrix */
/* An identity matrix we use to perform the equivalant of glLoadIdentity */
const GLfloat identitymatrix[16] = IDENTITY_MATRIX4;

/* The four vericies of a tetrahedron */
const GLfloat tetrahedron[4][3] = {
{ 1.0, 1.0, 1.0 }, /* index 0 */
{ -1.0, -1.0, 1.0 }, /* index 1 */
{ -1.0, 1.0, -1.0 }, /* index 2 */
{ 1.0, -1.0, -1.0 } }; /* index 3 */

/* Color information for each vertex */
const GLfloat colors[4][3] = {
{ 1.0, 0.0, 0.0 }, /* red */
{ 0.0, 1.0, 0.0 }, /* green */
{ 0.0, 0.0, 1.0 }, /* blue */
{ 1.0, 1.0, 1.0 } }; /* white */

const GLubyte tetraindicies[6] = { 0, 1, 2, 3, 0, 1 };

/* These pointers will receive the contents of our shader source code files */
GLchar *vertexsource, *fragmentsource, *geometrysource;

/* These are handles used to reference the shaders */
GLuint vertexshader, fragmentshader, geometryshader;

/* This is a handle to the shader program */
GLuint shaderprogram;

/* Allocate and assign a Vertex Array Object to our handle */
glGenVertexArrays(1, &vao);

/* Bind our Vertex Array Object as the current used object */
glBindVertexArray(vao);

/* Allocate and assign three Vertex Buffer Objects to our handle */
glGenBuffers(3, vbo);

/* Bind our first VBO as being the active buffer and storing vertex attributes (coordinates) */
glBindBuffer(GL_ARRAY_BUFFER, vbo[0]);

/* Copy the vertex data from tetrahedron to our buffer */
/* 12 * sizeof(GLfloat) is the size of the tetrahedrom array, since it contains 12 GLfloat values */
glBufferData(GL_ARRAY_BUFFER, 12 * sizeof(GLfloat), tetrahedron, GL_STATIC_DRAW);

/* Specify that our coordinate data is going into attribute index 0, and contains three floats per vertex */
glVertexAttribPointer((GLuint)0, 3, GL_FLOAT, GL_FALSE, 0, 0);

/* Enable attribute index 0 as being used */
glEnableVertexAttribArray(0);

/* Bind our second VBO as being the active buffer and storing vertex attributes (colors) */
glBindBuffer(GL_ARRAY_BUFFER, vbo[1]);

/* Copy the color data from colors to our buffer */
/* 12 * sizeof(GLfloat) is the size of the colors array, since it contains 12 GLfloat values */
glBufferData(GL_ARRAY_BUFFER, 12 * sizeof(GLfloat), colors, GL_STATIC_DRAW);

/* Specify that our color data is going into attribute index 1, and contains three floats per vertex */
glVertexAttribPointer((GLuint)1, 3, GL_FLOAT, GL_FALSE, 0, 0);

/* Enable attribute index 1 as being used */
glEnableVertexAttribArray(1);

/* Bind our third VBO as being the active buffer and storing vertex array indicies */
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, vbo[2]);

/* Copy the index data from tetraindicies to our buffer
* 6 * sizeof(GLubyte) is the size of the index array, since it contains 6 GLbyte values */

glBufferData(GL_ELEMENT_ARRAY_BUFFER, 6 * sizeof(GLubyte), tetraindicies, GL_STATIC_DRAW);

/* Read our shaders into the appropriate buffers */
vertexsource = filetobuf("tutorial4.vert");
geometrysource = filetobuf("tutorial4.geom");
fragmentsource = filetobuf("tutorial4.frag");

/* Assign our handles a "name" to new shader objects */
vertexshader = glCreateShader(GL_VERTEX_SHADER);
geometryshader = glCreateShader(GL_GEOMETRY_SHADER);
fragmentshader = glCreateShader(GL_FRAGMENT_SHADER);

/* Associate the source code buffers with each handle */
glShaderSource(vertexshader, 1, (const GLchar**)&vertexsource, 0);
glShaderSource(geometryshader, 1, (const GLchar**)&geometrysource, 0);
glShaderSource(fragmentshader, 1, (const GLchar**)&fragmentsource, 0);

/* Compile our shader objects */
glCompileShader(vertexshader);
glCompileShader(geometryshader);
glCompileShader(fragmentshader);

/* Assign our program handle a "name" */
shaderprogram = glCreateProgram();

/* Attach our shaders to our program */
glAttachShader(shaderprogram, vertexshader);
glAttachShader(shaderprogram, geometryshader);
glAttachShader(shaderprogram, fragmentshader);

/* Bind attribute 0 (coordinates) to in_Position and attribute 1 (colors) to in_Color */
glBindAttribLocation(shaderprogram, 0, "in_Position");
glBindAttribLocation(shaderprogram, 1, "in_Color");

/* Link our program, and set it as being actively used */
glLinkProgram(shaderprogram);
glUseProgram(shaderprogram);

/* Create our projection matrix with a 45 degree field of view
* a width to height ratio of 1 and view from .1 to 100 infront of us */

perspective(projectionmatrix, 45.0, 1.0, 0.1, 100.0);

/* Loop our display rotating our model more each time. */
for (i=0; i < 360; i++)
{
/* Load the identity matrix into modelmatrix. rotate the model, and move it back 5 */
memcpy(modelmatrix, identitymatrix, sizeof(GLfloat) * 16);
rotate(modelmatrix, (GLfloat)i * -1.0, X_AXIS);
rotate(modelmatrix, (GLfloat)i * 1.0, Y_AXIS);
rotate(modelmatrix, (GLfloat)i * 0.5, Z_AXIS);
translate(modelmatrix, 0, 0, -5.0);

/* multiply our modelmatrix and our projectionmatrix. Results are stored in modelmatrix */
multiply4x4(modelmatrix, projectionmatrix);

/* Bind our modelmatrix variable to be a uniform called mvpmatrix in our shaderprogram */
glUniformMatrix4fv(glGetUniformLocation(shaderprogram, "mvpmatrix"), 1, GL_FALSE, modelmatrix);

/* Make our background black */
glClearColor(0.0, 0.0, 0.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

/* Invoke glDrawElements telling it to draw a triangle strip using 6 indicies */
glDrawElements(GL_TRIANGLE_STRIP, 6, GL_UNSIGNED_BYTE, 0);

/* Swap our buffers to make our changes visible */
SDL_GL_SwapWindow(window);

/* Sleep for roughly 33 milliseconds between frames */
//SDL_Delay(33);
}

/* Cleanup all the things we bound and allocated */
glUseProgram(0);
glDisableVertexAttribArray(0);
glDisableVertexAttribArray(1);
glDetachShader(shaderprogram, vertexshader);
glDetachShader(shaderprogram, geometryshader);
glDetachShader(shaderprogram, fragmentshader);
glDeleteProgram(shaderprogram);
glDeleteShader(vertexshader);
glDeleteShader(geometryshader);
glDeleteShader(fragmentshader);
glDeleteBuffers(3, vbo);
glDeleteVertexArrays(1, &vao);
free(vertexsource);
free(geometrysource);
free(fragmentsource);
}

void destroywindow(SDL_WindowID window, SDL_GLContext context)
{
SDL_GL_DeleteContext(context);
SDL_DestroyWindow(window);
SDL_Quit();
}

/* Our program's entry point */
int main(int argc, char *argv[])
{
SDL_WindowID mainwindow; /* Our window handle */
SDL_GLContext maincontext; /* Our opengl context handle */

/* Create our window, opengl context, etc... */
setupwindow(&mainwindow, &maincontext);

/* Call our function that performs opengl operations */
drawscene(mainwindow);

/* Delete our opengl context, destroy our window, and shutdown SDL */
destroywindow(mainwindow, maincontext);

return 0;
}





myopenglextensions.h

//---------------------------------------------------------------------------

#ifndef MyOpenGLExtensionsH
#define MyOpenGLExtensionsH


#ifndef GLHEADERS
#define GLHEADERS
#include <windows.h>
#include <gl\gl.h>
#include <gl\glext.h>
#endif

//int initGLExtensions(); //function prototype

PFNGLCREATESHADERPROC glCreateShader;
PFNGLSHADERSOURCEPROC glShaderSource;
PFNGLCOMPILESHADERPROC glCompileShader;
.
.
.
PFNGLUNIFORMMATRIX4FVPROC glUniformMatrix4fv;



int initGLExtensions()
{
glCreateShader = (PFNGLCREATESHADERPROC) wglGetProcAddress("glCreateShader");
glShaderSource = (PFNGLSHADERSOURCEPROC) wglGetProcAddress("glShaderSource");
glCompileShader = (PFNGLCOMPILESHADERPROC) wglGetProcAddress("glCompileShader");
glCreateProgram = (PFNGLCREATEPROGRAMPROC) wglGetProcAddress("glCreateProgram");
.
.
.
glDeleteVertexArrays = (PFNGLDELETEVERTEXARRAYSPROC) wglGetProcAddress("glDeleteVertexArrays");

glUniformMatrix4fv = (PFNGLUNIFORMMATRIX4FVPROC) wglGetProcAddress("glUniformMatrix4fv");

if(glGenVertexArrays == NULL)
{
int x =0;
}


if (glCreateShader == NULL || glShaderSource == NULL || glCompileShader == NULL
|| glCreateProgram == NULL || glAttachShader == NULL || glLinkProgram == NULL
|| glUseProgram==NULL || glGetShaderiv == NULL || glDetachShader == NULL
|| glDeleteShader == NULL || glDeleteProgram == NULL || glIsShader == NULL
|| glIsProgram == NULL || glGetUniformLocation == NULL || glUniform1f == NULL
|| glUniform1i == NULL
)
{
return 0;
}
else if(glGenBuffers == NULL || glGenFramebuffers == NULL || glBindBuffer == NULL || glBindFramebuffer == NULL
|| glGenRenderbuffers == NULL || glBindRenderbuffer == NULL || glRenderbufferStorage == NULL
|| glFramebufferTexture2D == NULL || glFramebufferRenderbuffer == NULL || glCheckFramebufferStatus == NULL
|| glDeleteFramebuffers == NULL|| glDeleteRenderbuffers == NULL || glActiveTexture == NULL
|| glBufferData == NULL || glDrawBuffers == NULL || glDeleteBuffers == NULL
)
{
return 0;
}
else if(glVertexAttribPointer == NULL || glEnableVertexAttribArray == NULL || glDisableVertexAttribArray == NULL
|| glBindAttribLocation == NULL || glClampColor == NULL || glMultiTexCoord2f == NULL
|| glGenVertexArrays == NULL || glBindVertexArray==NULL || glDeleteVertexArrays==NULL)
{
return 0;
}

else if(glUniformMatrix4fv == NULL)
{
return 0;
}

return 1;
}


#endif





utils.cpp

#pragma hdrstop
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define GL3_PROTOTYPES 1
#include <GL3/gl3.h>
#include <SDL/SDL.h>
#include <math.h>

#include "utils.h"

/* Multiply 4x4 matrix m1 by 4x4 matrix m2 and store the result in m1 */
void multiply4x4(GLfloat *m1, GLfloat *m2)
{
GLfloat temp[16];

int x,y;

for (x=0; x < 4; x++)
{
for(y=0; y < 4; y++)
{
temp[y + (x*4)] = (m1[x*4] * m2[y]) +
(m1[(x*4)+1] * m2[y+4]) +
(m1[(x*4)+2] * m2[y+8]) +
(m1[(x*4)+3] * m2[y+12]);
}
}

memcpy(m1, temp, sizeof(GLfloat) * 16);
}

/* Generate a perspective view matrix using a field of view angle fov,
* window aspect ratio, near and far clipping planes */

void perspective(GLfloat *matrix, GLfloat fov, GLfloat aspect, GLfloat nearz, GLfloat farz)
{
GLfloat range;

range = tan(fov * 0.00872664625) * nearz; /* 0.00872664625 = PI/360 */
memset(matrix, 0, sizeof(GLfloat) * 16);
matrix[0] = (2 * nearz) / ((range * aspect) - (-range * aspect));
matrix[5] = (2 * nearz) / (2 * range);
matrix[10] = -(farz + nearz) / (farz - nearz);
matrix[11] = -1;
matrix[14] = -(2 * farz * nearz) / (farz - nearz);
}

/* Perform translation operations on a matrix */
void translate(GLfloat *matrix, GLfloat x, GLfloat y, GLfloat z)
{
GLfloat newmatrix[16] = IDENTITY_MATRIX4;

newmatrix[12] = x;
newmatrix[13] = y;
newmatrix[14] = z;

multiply4x4(matrix, newmatrix);
}

/* Rotate a matrix by an angle on a X, Y, or Z axis */
void rotate(GLfloat *matrix, GLfloat angle, AXIS axis)
{
const GLfloat d2r = 0.0174532925199; /* PI / 180 */
const int cos1[3] = { 5, 0, 0 };
const int cos2[3] = { 10, 10, 5 };
const int sin1[3] = { 6, 2, 1 };
const int sin2[3] = { 9, 8, 4 };
GLfloat newmatrix[16] = IDENTITY_MATRIX4;

newmatrix[cos1[axis]] = cos(d2r * angle);
newmatrix[sin1[axis]] = -sin(d2r * angle);
newmatrix[sin2[axis]] = -newmatrix[sin1[axis]];
newmatrix[cos2[axis]] = newmatrix[cos1[axis]];

multiply4x4(matrix, newmatrix);
}

/* A simple function that will read a file into an allocated char pointer buffer */
char* filetobuf(char *file)
{
FILE *fptr;
long length;
char *buf;

fptr = fopen(file, "r"); /* Open file for reading */
if (!fptr) /* Return NULL on failure */
return NULL;
fseek(fptr, 0, SEEK_END); /* Seek to the end of the file */
length = ftell(fptr); /* Find out how many bytes into the file we are */
buf = (char*)malloc(length + 1); /* Allocate a buffer for the entire length of the file plus a null terminator */
fseek(fptr, 0, SEEK_SET); /* Go back to the beginning of the file */
fread(buf, length, 1, fptr); /* Read the contents of the file in to the buffer */
fclose(fptr); /* Close the file */
buf[length] = 0; /* Null terminator */

return buf; /* Return the buffer */
}

/* A simple function that prints a message, the error code returned by SDL, and quits the application */
void sdldie(char *msg)
{
printf("%s: %s\n", msg, SDL_GetError());
SDL_Quit();
exit(1);
}




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forgive me if i'm wrong but shouldn't:
glDrawElements(GL_TRIANGLE_STRIP, 6, GL_UNSIGNED_BYTE, 0);
Contain a pointer to your object you want to draw?
Nowhere in your drawscene() function do you actually draw the things you defined. (as far as i can see, i'm by no means a pro)

Alex

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Setting the glDrawElements pointer to 0 is fine as long as the vbo is active with glBindBufferARB, at least in OpenGL 2.1.

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