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BlinksTale

OpenGL
glEnable(GL_TEXTURE_2D) inconsistent?

3 posts in this topic

Hello again GameDev! Turning to you guys with technical questions again, as I'm caught somewhere between reports on memory leaks (using Visual Leak Detector) and textures that will not consistently appear. Leak Detector's reports seeem to come up around my use of draw calls for indices of in quantities of about 10,000 or so, and return an issue regarding reusing memory location 0x00000000 (zero count not precise, having trouble getting the same error now, as it was also inconsistent) and my game is working in a way similar to how it did in the past before fixing other memory leaks (portions breaking in specific ways - falling through the floor when trying to load the next level, but changing none of the visuals). It's a custom 3D OpenGL engine I made, and I'm trying to stick PNGs on top of it now before Wednesday.... so switching to GLSL at this point isn't much of an option before the due date. Really, just trying to get GL_TEXTURE_2D working before then.

So the problem: I draw two or three textures on screen at the end of every custom display loop, based on PNGs with transparent backgrounds, using lodePNG to do so (a quick file set that works really well for just getting PNGs in, and that's it. No fancy loading bits), only sometimes the PNG textures show up as light yellow or pure white boxes of the same size (probably pure white, just hard for me to tell and screenshots aren't working) and other times they completely refuse to show up. Strangest yet is it differs from texture to texture, and sometimes one shows up fine and the other never appears, or they'll show up but freeze, or freeze and some combination of appearing well, appearing as white boxes, or not showing up.

I think it has to do with glEnable(GL_TEXTURE_2D) since moving that around influences other elements. I used to have a problem where the screen would flash a silhouette of the 3D models when leaving PNG mode (the pause screen) but got rid of that by putting glDisable(GL_TEXTURE_2D) at the beginning of every new draw call, and not putting it at the end even though usually it's main draw calls, glEnable(GL_TEXTURE_2D), pause menu draw calls/PNG usage, glDisable(GL_TEXTURE_2D).

Anyways, I'm probably butchering all that. Here's some code to clear things up:

[CODE]
void display() {
glScissor(0,0,windowWidth,windowHeight);
glViewport(0,0,windowWidth,windowHeight);

// Make sure background is black first, then draw on top of it
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // do not understand order, but this works

// Drawing all player views
for (int i=0; i<getPlayerCount(); i++) {
if (getPlayerPlayable(i)) {
// First take care of remnants from last menu
glDisable(GL_TEXTURE_2D);

// Four player splitscreen vals
int posX = windowWidth/2*(i==1 || i==3);
int posY = windowHeight/2*(i==2 || i==3);
int viewW = windowWidth*1/2;
int viewH = windowHeight*1/2;
glScissor(posX,posY,viewW,viewH);
glViewport(posX, posY, viewW, viewH);

// custom draw commands for view of 3D world
displayFor(i);

// Menu drawing
glEnable(GL_TEXTURE_2D);
drawMenu(i);
}
}
glutSwapBuffers();
}[/CODE]

And since it's referenced, may as well throw in displayFor too:

[CODE]
// Draw an entire player's screen
void displayFor(int player) {
// Paint background cyan to neon blue
glClearColor(getMapRed(), getMapGreen(), getMapBlue(), 0.0f); // do this here to allow black borders

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_MODELVIEW); // must set this here to undo silhouette's effects later
glLoadIdentity();

/* Push Matrix, scale, rotate, translate, and draw vertices go in here with different calls, then a pop matrix to end it */
/* There's also a shadow function in there with some stuff I'm not fully comfortable with yet, will post that if needed */
}[/CODE]

So finally, the drawMenu function

[CODE]
// Draws the 2D PNGs themselves as textures
void drawMenu(int i) {
// Don't use whole viewport since different menu for every player
//glViewport(0, 0, windowWidth, windowHeight); // don't need?
glMatrixMode(GL_PROJECTION); // necessary
glLoadIdentity(); // this one seems to be necessary
// Actual dimensions compared to expected dimensions (for now, my screen fullscreen)
GLfloat aspect = ((GLfloat)windowWidth / (GLfloat)windowHeight)/(1600.0/1050.0);
//gluPerspective(45.0, aspect*windowWidth/windowHeight, 0.050, 100.0);
if (aspect > 1.0) {
glOrtho(0, 1600*aspect, 1050, 0, -1, 1); // necessary
} else {
glOrtho(0, 1600, 1050/aspect, 0, -1, 1); // necessary
}
//glOrtho(0, 1600*aspect, 1050, 0, -1, 1); // necessary
glMatrixMode(GL_MODELVIEW); // don't need?
glLoadIdentity(); // don't need?

glDisable(GL_CULL_FACE);
//glDisable(GL_DEPTH_TEST);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_BLEND);
glDisable(GL_ALPHA_TEST); // no visible effect yet

// Enable the texture for OpenGL.
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); // slight smoothing when smaller than norm
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); // no smoothing when full size and up

// Still unsure of functionality, but known importance!
// glColor4ub brings back color to the PNG where it was black before
glColor4ub(255, 255, 255, 255);
// Where the logo is for bouncing/rotating
int time;
time = clock();

// Only draw any of it if paused
if (!getGameplayRunning()) {
// Start screen?
if (getLastPause() == -1) {
logoImage.draw(20.0*sin(time/1600.0),50+10.0*sin(time/800.0),aspect,false);
// Blink the press start/enter image
if (time%1200 < 900) {
if (joystickConnected()) {
pressStartImage.draw(0,700,aspect,false);
} else {
pressEnterImage.draw(0,700,aspect,false);
}
}
// Regular pause!
} else {
int option = getOption(i); // Option currently selected
float rotation = 5.0*sin(time/300.0); // Selected option rotates back and forth
resumeImage.draw(0,25,aspect,(option==0)*rotation);
creditsImage.draw(0,325,aspect,(option==1)*rotation); // will be options later
quitImage.draw(0,625,aspect,(option==2)*rotation);
}
}
glDisable(GL_BLEND);
glEnable(GL_ALPHA_TEST);
// depth test removed, was enabled here and disabled above, caused flashing
//glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);

}[/CODE]

Er, and I guess you want to see how my Image class works too. This is it, I promise!

[CODE]
#include "image.h"
#ifdef __APPLE_CC__
#include <GLUT/glut.h>
#else
#include <GL/glut.h>
#endif
#include "lodepng.h" // for 2D images, all PNG based for transparency
// lodePNG copyright (c) 2005-2012 Lode Vandevenne
#include <iostream> // for couts
using namespace std;
// No file name? Hardly an image now is it.
Image::Image() {
u2 = 0;
u3 = 0;
v2 = 0;
v3 = 0;
}
// Constructor! Take a file name in
Image::Image(const char* name) {
unsigned error1 = lodepng::decode(texture, width, height, name);

// Texture size must be power of two for the primitive OpenGL version this is written for. Find next power of two.
u2 = 1; while(u2 < width) u2 *= 2;
v2 = 1; while(v2 < height) v2 *= 2;
// Ratio for power of two version compared to actual version, to render the non power of two image with proper size.
u3 = (double)width / u2;
v3 = (double)height / v2;
}
// Draw self at a location
void Image::draw(int x, int y, float aspect, float rotate) {

// Would like to move this out of draw if possible
// Make power of two version of the image.
std::vector<unsigned char> image2(u2 * v2 * 4);
for(size_t y = 0; y < height; y++)
for(size_t x = 0; x < width; x++)
for(size_t c = 0; c < 4; c++)
{
image2[4 * u2 * y + 4 * x + c] = texture[4 * width * y + 4 * x + c];
}
glTexImage2D(GL_TEXTURE_2D, 0, 4, u2, v2, 0, GL_RGBA, GL_UNSIGNED_BYTE, &image2[0]);

float currentTextureX = x;
float currentTextureY = y;
//glTranslatef(0.0,0.0,10.0);
glPushMatrix();
// Always keep in center of screen, regardless of size/resolution
// And use aspect from earlier to do this, and 1600 as expected/base width
if (aspect > 1.0) {
glTranslatef(1600*aspect/2+currentTextureX, 0.0f+height/2+currentTextureY,0.0f);
} else {
glTranslatef(1600/2+currentTextureX, 0.0f+height/2+currentTextureY,0.0f);
}
glPushMatrix();
glRotatef(rotate,0.0,0.0,1.0);
// Draw the texture on a quad, using u3 and v3 to correct non power of two texture size.
glBegin(GL_QUADS);
glTexCoord2d( 0, 0); glVertex2f(0-width/2.0, 0-height/2.0);
glTexCoord2d(u3, 0); glVertex2f(0+width/2.0, 0-height/2.0);
glTexCoord2d(u3, v3); glVertex2f(0+width/2.0, 0+height/2.0);
glTexCoord2d( 0, v3); glVertex2f(0-width/2.0, 0+height/2.0);
glEnd();
glPopMatrix();
glPopMatrix();
}[/CODE]

Thanks guys! I know this is a lot of code to provide... but I'm really not sure how to cut it down more than that at this point.
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I only glanced through your code, but what I immediately saw:[list=1]
[*]Do not use glTexImage2D in every frame! Use glGenTextures in constructor and then glBindTexture whenever you build or use it.
[*]You should use GL_RGBA instead of "4". The latter is relict from OpenGL 1.0 era.
[/list]
But neither of these problems should cause the textures to not to draw.
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glEnable(GL_TEXTURE_2D) doesn't cause memeory leaks.
You might have a leak with your PNG loading code. In order to be sure, try replacing it with a hardcoded 1x1 texture.
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All-white textures is normally a sign that you're using non-power-of-two textures on hardware that doesn't support them, but you've already got checks for that so the next issue is likely to be incomplete or otherwise invalid textures. Can you confirm a few things before proceeding?

- You don't seem to be calling glGenTextures or glBindTexture anywhere. This just means that your glTexImage call will modify the default texture object (0) but is this behaviour intentional?

- Similarly, are you aware that glTexParameter is part of the properties of the currently bound texture object, not global state? So if you are binding textures anywhere else in your code, those glTexParameter calls are actually not affecting those textures you bind.

- Have you checked your texture size against GL_MAX_TEXTURE_SIZE?

Regarding the memory leaks you're detecting, one likely explanation is that you don't actually have any. As soon as you start writing OpenGL code you've moved outside of the realms of software - you're now using hardware resources in GPU memory managed by your OpenGL driver, not by your program, and - since OpenGL doesn't specify how drivers manage memory - the driver is free to pull all manner of tricks, one of which may be (not saying this is what's happening here, just providing an example) not immediately freeing memory but leaving it hanging around for a while in case something else in your program may need to re-use it shortly. So a software-based leak detector is just going to feed you wrong information and put you on the wrong track.
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