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I'm trying to map a generated 2D texture on a quad. So far the quad is rendered, but it is gray if I don't set a color and if I set colors for the vertices it shows the colors, yet the texture is not shown.
The reason for using fixed pipeline instead of shaders is that in order to generate the texture I would have to pass too much data to the shaders to generate the texture efficiently. So ideally I do not want to have a shader for something that should be as simple as rendering a texture on a quad. Although the program uses shaders extensively.
I tried using GLubyte for passing the data to glTexImage2D but got the same result. Also I tried various positions to call glEnable(GL_TEXTURE_2D), glBindTexture, glTexParameteri and glTexImage2D.
Furthermore, I commented glTexEnvf, glBindTexture (unbinding), glDisable(GL_TEXTURE_2D) and glDeleteTextures(...).
All with the same result.
Maybe it is not possible to use fixed pipeline texture rendering in a program that also uses shaders? Or did I make a mistake in my code? As far as I can see and according to Google the code below should render the texture on the quad. It is bugging me for a few days nows and probably it is a simple mistake...
glGetError returns 0 at all positions in the snippet.
std::cout<<glGetError()<<std::endl;
GLuint texName;
glGenTextures(1, &texName);
glBindTexture(GL_TEXTURE_2D, texName);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
std::cout<<glGetError()<<std::endl;
GLfloat image[64][64][4];
for(unsigned int i = 0; i<64; i++)
{
for(unsigned int j = 0; j<64; j++)
{
image[i][j][0] = 1.0f;
image[i][j][1] = 0.5f;
image[i][j][2] = (float)i/64;
image[i][j][3] = 1.0f;
}
}
std::cout<<glGetError()<<std::endl;
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 64,
64, 0, GL_RGBA, GL_FLOAT,
image);
std::cout<<glGetError()<<std::endl;
glEnable(GL_TEXTURE_2D);
glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE,GL_REPLACE);
glBindTexture(GL_TEXTURE_2D, texName);
glBegin(GL_QUADS);
glTexCoord2f(0, 0); glVertex2i(10, 10);
glTexCoord2f(0, 1); glVertex2i(10, 110);
glTexCoord2f(1, 1); glVertex2i(110, 110);
glTexCoord2f(1, 0); glVertex2i(110, 10);
glEnd();
glBindTexture(GL_TEXTURE_2D, 0);
glDisable(GL_TEXTURE_2D);
glDeleteTextures(1, &texName);
std::cout<<glGetError()<<std::endl;
I should have mentioned in my question that I wanted the texture to be on the screen (in 2D).
A collegue was able to help me and suggested to use glDrawPixels which works, without disabling the shaders running (I didn't know they had to be disabled since most fixed pipeline stuff seemed to work, so thank you Bahbar).
I have been having a very odd problem when trying to use OpenGL's C++ API. I am trying to load in a texture using ImageMagick, and then display it as a simple 2D textured square. I have a decent amount of experience with using OpenGL in Java, so I understand how to render a texture and bind it to a primitive. However, each time I attempt to draw it, the program either fails to render, or it renders it as a (properly sized) white square. I'm not entirely sure what is going on, but I believe it has to do with ImageMagick.
I have been using Ubuntu's terminal for compiling, and I've learned just how painful it can be to have to install libraries manually. ImageMagick first refused to compile when used in my program, and when I finally got the program to compile, it would seg-fault each time it ran. I've finally got it "working", but now, whenever I attempt to load in the image, the program will run without rendering. I haven't found anything like this on Google.
http://imgur.com/C7yKwDK
The odd thing is, very rarely, it will work correctly and render the square as expected. However, when I then try to rerun the program, it fails as shown above. I've determined that the line that causes it to fail to render is the same line the image is loaded, so that led me to believe that the image was just being loaded incorrectly, causing the program to fail. However, if I move the texture loading code before the creation of the GL window, the program will consistently render successfully, but the textured square appears only as white (though the size of the square is correct, so I know the image loading is working).
Anyway, sorry for the long post. I've just given up solving this one on my own, and was hoping one of you could help me out.
OpenGL Initialization Code:
Texture* tx;
void GraphicsOGL :: initialize3D(int argc, char* argv[]) {
Magick::InitializeMagick(*argv);
glutInit(&argc, argv);
//Loading Here ALWAYS Causes White Square
/*glEnable(GL_TEXTURE_2D);
tx = new Texture("Resources/Images/test.png");
tx->load();*/
glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
glutInitWindowSize(SCREEN_WIDTH, SCREEN_HEIGHT);
glutInitWindowPosition(100, 100);
glutCreateWindow("OpenGL Game");
glViewport(0,0,SCREEN_WIDTH,SCREEN_HEIGHT);
glOrtho(0,SCREEN_WIDTH,SCREEN_HEIGHT,0, -3,1000);
glEnable(GL_DEPTH_TEST);
glEnable(GL_ALPHA_TEST);
glEnable(GL_TEXTURE_2D);
//Loading Here SOMETIMES Works, But Typically Fails
tx = new Texture("Resources/Images/test.png");
tx->load();
glutDisplayFunc(displayCallback);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glutMainLoop();
}
Texture Loading Code:
bool Texture::load() {
try {
m_image.read(m_fileName); //This Line Causes it to Fail to Render
m_image.write(&m_blob, "RGBA");
}
catch (Magick::Error& Error) {
std::cout << "Error loading texture '" << m_fileName << "': " << Error.what() << std::endl;
return false;
}
width = m_image.columns();
height = m_image.rows();
glGenTextures(1, &m_textureObj);
glBindTexture(m_textureTarget, m_textureObj);
//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_BASE_LEVEL, 0);
//glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAX_LEVEL, 0);
glTexParameterf(m_textureTarget, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameterf(m_textureTarget, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
glTexParameterf(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
glTexParameteri(GL_TEXTURE_2D, GL_GENERATE_MIPMAP, GL_TRUE);
glTexImage2D(m_textureTarget, 0, GL_RGBA, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, m_blob.data());
//glBindTexture(m_textureTarget, 0);
return true;
}
Texture Drawing Code:
void GraphicsOGL :: drawTexture(float x, float y, Texture* tex) {
glEnable(GL_TEXTURE_2D);
tex->bind();
float depth = 0, w, h;
w = tex->getWidth();
h = tex->getHeight();
glBegin(GL_QUADS);
glVertex3f(x, y+h, depth); glTexCoord2f(1,0);
glVertex3f(x+w, y+h, depth); glTexCoord2f(1,1);
glVertex3f(x+w, y, depth); glTexCoord2f(0,1);
glVertex3f(x, y, depth); glTexCoord2f(0,0);
glEnd();
}
I'm having some weird memory issues in a C program I'm writing, and I think something related to my texture loading system is the cause.
The problem is that, depending on how many textures I make, different issues start coming up. Less textures tend to ever so slightly change other variables in the program. If I include all the textures I want to include, the program may spit out a host of different "* glibc detected *" type errors, and occasionally a Segmentation Fault.
The kicker is that occasionally, the program works perfectly. It's all the luck of the draw.
My code is pretty heavy at this point, so I'll just post what I believe to be the relevant parts of it.
d_newTexture(d_loadBMP("resources/sprites/default.bmp"), &textures);
Is the function I call to load a texture into OpenGL. "textures" is a variable of type texMan_t, which is a struct I made.
typedef struct {
GLuint texID[500];
int texInc;
} texMan_t;
The idea is that texMan_t encompasses all your texture IDs for easier use. texInc just keeps track of what the next available member of texID is.
This is d_newTexture:
void d_newTexture(imgInfo_t info, texMan_t* tex) {
glEnable(GL_TEXTURE_2D);
glGenTextures(1, &tex->texID[tex->texInc]);
glBindTexture(GL_TEXTURE_2D, tex->texID[tex->texInc]);
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
gluBuild2DMipmaps( GL_TEXTURE_2D, 4, info.width, info.height, GL_RGBA, GL_UNSIGNED_BYTE, info.data );
tex->texInc++;
glDisable(GL_TEXTURE_2D);
}
I also use a function by the name of d_newTextures, which is identical to d_newTexture, except for that it splits up a simple sprite sheet into multiple textures.
void d_newTextures(imgInfo_t info, int count, texMan_t* tex) {
glEnable(GL_TEXTURE_2D);
glGenTextures(count, &tex->texID[tex->texInc]);
for(int i=0; i<count; i++) {
glBindTexture(GL_TEXTURE_2D, tex->texID[tex->texInc+i]);
glTexEnvf( GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
gluBuild2DMipmaps( GL_TEXTURE_2D, 4, info.width, info.height/count,
GL_RGBA, GL_UNSIGNED_BYTE, &info.data[info.width*(info.height/count)*4*i] );
}
tex->texInc+=count;
glDisable(GL_TEXTURE_2D);
}
What could be the cause of the issues I'm seeing?
EDIT: Recently, I've also been getting the error "* glibc detected out/PokeEngine: free(): invalid pointer: 0x01010101 **" after closing the program as well, assuming it's able to properly begin. The backtrace looks like this:
/lib/i386-linux-gnu/libc.so.6(+0x75ee2)[0xceeee2]
/usr/lib/nvidia-173/libGLcore.so.1(+0x277c7c)[0x109ac7c]
EDIT 2:
Here's the code for d_loadBMP as well. Hope it helps!
imgInfo_t d_loadBMP(char* filename) {
imgInfo_t out;
FILE * bmpFile;
bmpFile = fopen(filename, "r");
if(bmpFile == NULL) {
printf("ERROR: Texture file not found!\n");
}
bmp_sign bmpSig;
bmp_fHeader bmpFileHeader;
bmp_iHeader bmpInfoHeader;
fread(&bmpSig, sizeof(bmp_sign), 1, bmpFile);
fread(&bmpFileHeader, sizeof(bmp_fHeader), 1, bmpFile);
fread(&bmpInfoHeader, sizeof(bmp_iHeader), 1, bmpFile);
out.width = bmpInfoHeader.width;
out.height = bmpInfoHeader.height;
out.size = bmpInfoHeader.imageSize;
out.data = (char*)malloc(sizeof(char)*out.width*out.height*4);
// Loaded backwards because that's how BMPs are stored
for(int i=out.width*out.height*4; i>0; i-=4) {
fread(&out.data[i+2], sizeof(char), 1, bmpFile);
fread(&out.data[i+1], sizeof(char), 1, bmpFile);
fread(&out.data[i], sizeof(char), 1, bmpFile);
out.data[i+3] = 255;
}
return out;
}
The way you're loading BMP files is wrong. You're reading right into structs, which is very unreliable, because the memory layout your compiler chooses for a struct may vastly differ from the data layout in a file. Also your code contains zero error checks. If I had to make an educated guess I'd say this is where your problems are.
BTW. glEnable(GL_TEXTURE_…) enables a texture target as data source for rendering. It's completely unnecessary for just generating and uploading textures. You can omit the bracing glEnable(GL_TEXTURE_2D); … glDisable(GL_TEXTURE_2D) blocks in your loading code. Also I'd not use gluBuildMipmaps2D – it doesn't support arbitrary texture dimensions, and you're disabling mipmapping anyway – and just upload directly with glTexImage2D.
Also I don't get your need for a texture manager. Or at least not why your texture manager looks like this. A much better approach would be using a hash map file path → texture ID and a reference count.
I'm attempting to render a .png image as a texture. However, all that is being rendered is a white square.
I give my texture a unique int ID called texID, read the pixeldata into a buffer 'image' (declared in the .h file). I load my pixelbuffer, do all of my OpenGL stuff and bind that pixelbuffer to a texture for OpenGL. I then draw it all using glDrawElements.
Also I initialize the texture with a size of 32x32 when its contructor is called, therefore i doubt it is related to a power of two size issue.
Can anybody see any mistakes in my OpenGL GL_TEXTURE_2D setup that might give me a block white square.
#include "Texture.h"
Texture::Texture(int width, int height, string filename)
{
const char* fnPtr = filename.c_str(); //our image loader accepts a ptr to a char, not a string
printf(fnPtr);
w = width; //give our texture a width and height, the reason that we need to pass in the width and height values manually
h = height;//UPDATE, these MUST be P.O.T.
unsigned error = lodepng::decode(image,w,h,fnPtr);//lodepng's decode function will load the pixel data into image vector
//display any errors with the texture
if(error)
{
cout << "\ndecoder error " << error << ": " << lodepng_error_text(error) <<endl;
}
for(int i = 0; i<image.size(); i++)
{
printf("%i,", image.at(i));
}
printf("\nImage size is %i", image.size());
//image now contains our pixeldata. All ready for OpenGL to do its thing
//let's get this texture up in the video memory
texGLInit();
}
void Texture::texGLInit()
{
//WHERE YOU LEFT OFF: glGenTextures isn't assigning an ID to textures. it stays at zero the whole time
//i believe this is why it's been rendering white
glGenTextures(1, &textures);
printf("\ntexture = %u", textures);
glBindTexture(GL_TEXTURE_2D, textures);//evrything we're about to do is about this texture
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT);
//glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
//glDisable(GL_COLOR_MATERIAL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8,w,h,0, GL_RGBA, GL_UNSIGNED_BYTE, &image);
//we COULD free the image vectors memory right about now.
}
void Texture::draw(point centerPoint, point dimensions)
{
glEnable(GL_TEXTURE_2D);
printf("\nDrawing block at (%f, %f)",centerPoint.x, centerPoint.y);
glBindTexture(GL_TEXTURE_2D, textures);//bind the texture
//create a quick vertex array for the primitive we're going to bind the texture to
printf("TexID = %u",textures);
GLfloat vArray[8] =
{
centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2),//bottom left i0
centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top left i1
centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2),//top right i2
centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2)//bottom right i3
};
//create a quick texture array (we COULD create this on the heap rather than creating/destoying every cycle)
GLfloat tArray[8] =
{
0.0f,0.0f, //0
0.0f,1.0f, //1
1.0f,1.0f, //2
1.0f,0.0f //3
};
//and finally.. the index array...remember, we draw in triangles....(and we'll go CW)
GLubyte iArray[6] =
{
0,1,2,
0,2,3
};
//Activate arrays
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
//Give openGL a pointer to our vArray and tArray
glVertexPointer(2, GL_FLOAT, 0, &vArray[0]);
glTexCoordPointer(2, GL_FLOAT, 0, &tArray[0]);
//Draw it all
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_BYTE, &iArray[0]);
//glDrawArrays(GL_TRIANGLES,0,6);
//Disable the vertex arrays
glDisableClientState(GL_VERTEX_ARRAY);
glDisableClientState(GL_TEXTURE_COORD_ARRAY);
glDisable(GL_TEXTURE_2D);
//done!
/*glBegin(GL_QUADS);
glTexCoord2f(0.0f,0.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glTexCoord2f(0.0f,1.0f);
glVertex2f(centerPoint.x-(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,1.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y+(dimensions.y/2));
glTexCoord2f(1.0f,0.0f);
glVertex2f(centerPoint.x+(dimensions.x/2), centerPoint.y-(dimensions.y/2));
glEnd();*/
}
Texture::Texture(void)
{
}
Texture::~Texture(void)
{
}
I'll also include the main class' init, where I do a bit more OGL setup before this.
void init(void)
{
printf("\n......Hello Guy. \n....\nInitilising");
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0,XSize,0,YSize);
glEnable(GL_TEXTURE_2D);
myBlock = new Block(0,0,offset);
glClearColor(0,0.4,0.7,1);
glLineWidth(2); // Width of the drawing line
glMatrixMode(GL_MODELVIEW);
glDisable(GL_DEPTH_TEST);
printf("\nInitialisation Complete");
}
Update: adding in the main function where I first setup my OpenGL window.
int main(int argc, char** argv)
{
glutInit(&argc, argv); // GLUT Initialization
glutInitDisplayMode(GLUT_RGBA|GLUT_DOUBLE); // Initializing the Display mode
glutInitWindowSize(800,600); // Define the window size
glutCreateWindow("Gem Miners"); // Create the window, with caption.
printf("\n========== McLeanTech Systems =========\nBecoming Sentient\n...\n...\n....\nKILL\nHUMAN\nRACE \n");
init(); // All OpenGL initialization
//-- Callback functions ---------------------
glutDisplayFunc(display);
glutKeyboardFunc(mykey);
glutSpecialFunc(processSpecialKeys);
glutSpecialUpFunc(processSpecialUpKeys);
//glutMouseFunc(mymouse);
glutMainLoop(); // Loop waiting for event
}
Here's the usual checklist for whenever textures come out white:
OpenGL context created and being bound to current thread when attemting to load texture?
Allocated texture ID using glGenTextures?
Are the parameters format and internal format to glTex[Sub]Image… valid OpenGL tokens allowed as input for this function?
Is mipmapping being used?
YES: Supply all mipmap layers – optimally set glTexParameteri GL_TEXTURE_BASE_LEVEL and GL_TEXTURE_MAX_LEVEL, as well as GL_TEXTURE_MIN_LOD and GL_TEXTURE_MAX_LOG.
NO: Turn off mipmap filtering by setting glTexParameteri GL_TEXTURE_MIN_FILTER to GL_NEAREST or GL_LINEAR.
I've been attempting to render text onto an openGL window using SDL and the SDL_TTF library on windows XP, VS2010.
Versions:
SDL version 1.2.14
SDL TTF devel 1.2.10
openGL (version is at least 2-3 years old).
I have successfully created an openGL window using SDL / SDL_image and can render lines / polygons onto it with no problems.
However, moving onto text it appears that there is some flaw in my current program, I am getting the following result when trying this code here
for those not willing to pastebin here are only the crutial code segments:
void drawText(char * text) {
glLoadIdentity();
SDL_Color clrFg = {0,0,255,0}; // set colour to blue (or 'red' for BGRA)
SDL_Surface *sText = TTF_RenderUTF8_Blended( fntCourier, text, clrFg );
GLuint * texture = create_texture(sText);
glBindTexture(GL_TEXTURE_2D, *texture);
// draw a polygon and map the texture to it, may be the source of error
glBegin(GL_QUADS); {
glTexCoord2i(0, 0); glVertex3f(0, 0, 0);
glTexCoord2i(1, 0); glVertex3f(0 + sText->w, 0, 0);
glTexCoord2i(1, 1); glVertex3f(0 + sText->w, 0 + sText->h, 0);
glTexCoord2i(0, 1); glVertex3f(0, 0 + sText->h, 0);
} glEnd();
// free the surface and texture, removing this code has no effect
SDL_FreeSurface( sText );
glDeleteTextures( 1, texture );
}
segment 2:
// create GLTexture out of SDL_Surface
GLuint * create_texture(SDL_Surface *surface) {
GLuint texture = 0;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
// The SDL_Surface appears to have BGR_A formatting, however this ends up with a
// white rectangle no matter which colour i set in the previous code.
int Mode = GL_RGB;
if(surface->format->BytesPerPixel == 4) {
Mode = GL_RGBA;
}
glTexImage2D(GL_TEXTURE_2D, 0, Mode, surface->w, surface->h, 0, Mode,
GL_UNSIGNED_BYTE, surface->pixels);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
return &texture;
}
Is there an obvious bit of code I am missing?
Thank you for any help on this subject.
I've been trying to learn openGL and SDL for 3 days now, so please forgive any misinformation on my part.
EDIT:
I notice that using
TTF_RenderUTF8_Shaded
TTF_RenderUTF8_Solid
Throw a null pointer exception, meaning that there is an error within the actual text rendering function (I suspect), I do not know how this means TTF_RenderUTF8_Blended returns a red square but I suspect all troubles hinge on this.
I think the problem is in the glEnable(GL_TEXTURE_2D) and glDisable(GL_TEXTURE_2D) functions which must be called every time the text is painted on the screen.And maybe also the color conversion between the SDL and GL surface is not right.
I have combined create_texture and drawText into a single function that displays the text properly. That's the code:
void drawText(char * text, TTF_Font* tmpfont) {
SDL_Rect area;
SDL_Color clrFg = {0,0,255,0};
SDL_Surface *sText = SDL_DisplayFormatAlpha(TTF_RenderUTF8_Blended( tmpfont, text, clrFg ));
area.x = 0;area.y = 0;area.w = sText->w;area.h = sText->h;
SDL_Surface* temp = SDL_CreateRGBSurface(SDL_HWSURFACE|SDL_SRCALPHA,sText->w,sText->h,32,0x000000ff,0x0000ff00,0x00ff0000,0x000000ff);
SDL_BlitSurface(sText, &area, temp, NULL);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, sText->w, sText->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, temp->pixels);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS); {
glTexCoord2d(0, 0); glVertex3f(0, 0, 0);
glTexCoord2d(1, 0); glVertex3f(0 + sText->w, 0, 0);
glTexCoord2d(1, 1); glVertex3f(0 + sText->w, 0 + sText->h, 0);
glTexCoord2d(0, 1); glVertex3f(0, 0 + sText->h, 0);
} glEnd();
glDisable(GL_TEXTURE_2D);
SDL_FreeSurface( sText );
SDL_FreeSurface( temp );
}
screenshot
I'm initializing OpenGL as follows:
int Init(){
glClearColor( 0.1, 0.2, 0.2, 1);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
glOrtho( 0, 600, 300, 0, -1, 1 );
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
if( glGetError() != GL_NO_ERROR ){
return false;
}
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_COLOR, GL_ONE_MINUS_SRC_ALPHA);
}
I think you should just add glEnable(GL_BLEND), because the code for the text surface says TTF_RenderUTF8_Blended( fntCourier, text, clrFg ) and you have to enable the blending abilities of opengl.
EDIT
Okay, I finally took the time to put your code through a compiler. Most importantly, compiler with -Werror so that warning turn into errors
GLuint * create_texture(SDL_Surface *surface) {
GLuint texture = 0;
/*...*/
return &texture;
}
I didn't see it first, because that's something like C coder's 101 and is quite unexpected: You must not return pointers to local variables!. Once the functions goes out of scope the pointer returned will point to nonsense only. Why do you return a pointer at all? Just return a integer:
GLuint create_texture(SDL_Surface *surface) {
GLuint texture = 0;
/*...*/
return texture;
}
Because of this you're also not going to delete the texture afterward. You upload it to OpenGL, but then loose the reference to it.
Your code misses a glEnable(GL_TEXTURE_2D) that's why you can't see any effects of texture. However your use of textures is suboptimal. They way you did it, you recreate a whole new texture each time you're about to draw that text. If that happens in a animation loop, you'll
run out of texture memory rather soon
slow it down significantly
(1) can be addressed by not generating a new texture name each redraw
(2) can be addresses by uploading new texture data only when the text changes and by not using glTexImage2D, but glTexSubImage2D (of course, if the dimensions of the texture change, it must be glTexImage2D).
EDIT, found another possible issue, but first fix your pointer issue.
You should make sure, that you're using GL_REPLACE or GL_MODULATE texture environment mode. If using GL_DECAL or GL_BLEND you end up with red text on a red quad.
There was leaking memory of of the function in my previous post and the program was crashing after some time...
I improved this by separating the texture loading and displaying:
The first function must be called before the SDL loop.It loads text string into memory:
Every string loaded must have different txtNum parameter
GLuint texture[100];
SDL_Rect area[100];
void Load_string(char * text, SDL_Color clr, int txtNum, const char* file, int ptsize){
TTF_Font* tmpfont;
tmpfont = TTF_OpenFont(file, ptsize);
SDL_Surface *sText = SDL_DisplayFormatAlpha(TTF_RenderUTF8_Solid( tmpfont, text, clr ));
area[txtNum].x = 0;area[txtNum].y = 0;area[txtNum].w = sText->w;area[txtNum].h = sText->h;
glGenTextures(1, &texture[txtNum]);
glBindTexture(GL_TEXTURE_2D, texture[txtNum]);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA8, sText->w, sText->h, 0, GL_BGRA, GL_UNSIGNED_BYTE, sText->pixels);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
SDL_FreeSurface( sText );
TTF_CloseFont(tmpfont);
}
The second one displays the string, must be called in the SDL loop:
void drawText(float coords[3], int txtNum) {
glBindTexture(GL_TEXTURE_2D, texture[txtNum]);
glEnable(GL_TEXTURE_2D);
glBegin(GL_QUADS); {
glTexCoord2f(0, 0); glVertex3f(coords[0], coords[1], coords[2]);
glTexCoord2f(1, 0); glVertex3f(coords[0] + area[txtNum].w, coords[1], coords[2]);
glTexCoord2f(1, 1); glVertex3f(coords[0] + area[txtNum].w, coords[1] + area[txtNum].h, coords[2]);
glTexCoord2f(0, 1); glVertex3f(coords[0], coords[1] + area[txtNum].h, coords[2]);
} glEnd();
glDisable(GL_TEXTURE_2D);
}