Sign in to follow this  
energydrink

OpenGL [SOLVED] problems with render-to-texture

Recommended Posts

There seems to be problems when creating a texture dynamically that is larger than the screen size. I am just a rookie in OpenGL but there must be a problem with the glViewport call to resize it to fit the texture I am creating. Edit: I forgot to add, I am using glCopyTexImage2D. I have two images to show the problem. Ok Not ok As you can see where the small letters begin they are not displayed correctly when used. As for now, I am not using any call to glViewport at all because using glViewport( 0, 0, theWidthOfTexture, theHeightOfTexture ) displays nothing. Are there any pitfalls in using this or should I paste some code? [Edited by - energydrink on April 24, 2010 4:39:13 PM]

Share this post


Link to post
Share on other sites
I looked into FBO and yes, it is probably what I need. However, after reading up on the subject there seems not to working. I am sure there is a minor problem or have I missed the concept?

I am basically using the same code as with glCopyTexImage2D. The following code is only called once when creating a dynamic texture for a fontsheet.

Notice I have no texture parameters here

/*==============================
CREATE TEXTURE
==============================*/

myFontTexID.push_back( 0 ); //Allocate new space for texture reference
glGenTextures( 1, &myFontTexID[ myFontTexID.size() - 1 ] );
glBindTexture( GL_TEXTURE_2D, myFontTexID[ myFontTexID.size() - 1 ] );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, ( GLsizei )totalWidth, ( GLsizei )totalHeight, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL );


The following buffer setup should be correctly executed, right?

/*============================
BUFFER SETUP
============================*/

GLuint framebuffer;
glGenFramebuffers( 1, &framebuffer );
glBindFramebuffer( GL_FRAMEBUFFER_EXT, framebuffer );

GLuint renderbuffer;
glGenRenderbuffers( 1, &renderbuffer );
glBindRenderbuffer( GL_RENDERBUFFER_EXT, renderbuffer );

//Create storage for image data
glRenderbufferStorage( GL_RENDERBUFFER_EXT, GL_RGBA, ( GLsizei )totalWidth, ( GLsizei )totalHeight );
//Attach renderbuffer to currently bound framebuffer
glFramebufferRenderbuffer( GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, 0 );
//Attach texture to FBO
glFramebufferTexture2D( GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, myFontTexID[ myFontTexID.size() - 1 ], 0 );



Here is if I got the concept correctly. With glCopyTexImage2D it was easy to understand, it was basically a printscreen call. However with FBO I am now assuming that everything that gets rendered will be put into the renderbuffer which is attached to the framebuffer which is atteched to the "main"texture. There is no call like when using VBO like glBufferData where you actually have a command to upload the current information.

Since this is in the same method, the framebuffer should be already bound.

/*============================
DRAW TEXTURE
============================*/

glViewport( 0, 0, totalWidth, totalHeight ); //Set size of texture
enableTex2DAttrib();

GLfloat x = 0.0f;
GLuint tempTex;
glGenTextures( 1, &tempTex );
glBindTexture( GL_TEXTURE_2D, tempTex );

glClear( GL_COLOR_BUFFER_BIT ); //Clear everything before drawing
for( GLuint i = 0; i < myAsciiTable.length(); i++ ) {
character = myAsciiTable[ i ];

//Create temporary texture
SDL_Surface *tempSurf = TTF_RenderText_Blended( myLoadedFont, character.c_str(), color );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST );
glTexImage2D( GL_TEXTURE_2D, 0, GL_RGBA, tempSurf->w, tempSurf->h, 0, GL_RGBA, GL_UNSIGNED_BYTE, tempSurf->pixels );

//Advance one glyph size
glLoadIdentity();
glTranslatef( x, 0.0f, 0.0f );
x += ( GLfloat )tempSurf->w;

glBegin( GL_QUADS );
glTexCoord2f( 0.0f, 1.0f ); glVertex2f( 0.0f, 0.0f );
glTexCoord2f( 0.0f, 0.0f ); glVertex2f( 0.0f, ( GLfloat )tempSurf->h );
glTexCoord2f( 1.0f, 0.0f ); glVertex2f( ( GLfloat )tempSurf->w, ( GLfloat )tempSurf->h );
glTexCoord2f( 1.0f, 1.0f ); glVertex2f( ( GLfloat )tempSurf->w, 0.0f );
glEnd();

SDL_FreeSurface( tempSurf );
}
//Cleanup
glBindFramebuffer( GL_FRAMEBUFFER_EXT, 0 );

glPopAttrib();
glPopMatrix();

glViewport( 0, 0, SCREEN_WIDTH, SCREEN_HEIGHT );
glClear( GL_COLOR_BUFFER_BIT );

glDeleteFramebuffers( 1, &framebuffer );
glDeleteRenderbuffers( 1, &renderbuffer );



This displays only white quads with no texture. If you recall what I wrote before my "create texture" code, I have no texture parameters. Setting a MIN and MAG filter will just end up displaying nothing.

Help! :)

Share this post


Link to post
Share on other sites
You don't need a renderbuffer, just attach a texture to the FBO.
Set the MIN/MAG filters to something, like NEAREST, before glTexImage2D. Else, your texture will be incomplete (as the default is mipmapped, and you don't have mipmaps).

This should make it work.

Share this post


Link to post
Share on other sites
Thanks for fast reply. It sort of work. First it displays nothing, removing glViewport() will display text on the screen. However, the texture is larger than the screen and therefor not getting the whole texture. This was also the case when I used glCopyTexImage2D, using glViewport() would display nothing.

Using my "setOrtho2D" method was the only way to get it to work.

glViewport( 0, 0, width, height );
glMatrixMode( GL_PROJECTION );
glLoadIdentity();
gluOrtho2D( 0, width, 0, height );




Is there a reason I have to call my gluOrtho2D aswell? ( I am not using perspective, only 2D )

In anyway, it is working! Ah, finally! BIG thank you! :)
success

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

Sign in to follow this  

  • Forum Statistics

    • Total Topics
      627770
    • Total Posts
      2979002
  • Similar Content

    • By DelicateTreeFrog
      Hello! As an exercise for delving into modern OpenGL, I'm creating a simple .obj renderer. I want to support things like varying degrees of specularity, geometry opacity, things like that, on a per-material basis. Different materials can also have different textures. Basic .obj necessities. I've done this in old school OpenGL, but modern OpenGL has its own thing going on, and I'd like to conform as closely to the standards as possible so as to keep the program running correctly, and I'm hoping to avoid picking up bad habits this early on.
      Reading around on the OpenGL Wiki, one tip in particular really stands out to me on this page:
      For something like a renderer for .obj files, this sort of thing seems almost ideal, but according to the wiki, it's a bad idea. Interesting to note!
      So, here's what the plan is so far as far as loading goes:
      Set up a type for materials so that materials can be created and destroyed. They will contain things like diffuse color, diffuse texture, geometry opacity, and so on, for each material in the .mtl file. Since .obj files are conveniently split up by material, I can load different groups of vertices/normals/UVs and triangles into different blocks of data for different models. When it comes to the rendering, I get a bit lost. I can either:
      Between drawing triangle groups, call glUseProgram to use a different shader for that particular geometry (so a unique shader just for the material that is shared by this triangle group). or
      Between drawing triangle groups, call glUniform a few times to adjust different parameters within the "master shader", such as specularity, diffuse color, and geometry opacity. In both cases, I still have to call glBindTexture between drawing triangle groups in order to bind the diffuse texture used by the material, so there doesn't seem to be a way around having the CPU do *something* during the rendering process instead of letting the GPU do everything all at once.
      The second option here seems less cluttered, however. There are less shaders to keep up with while one "master shader" handles it all. I don't have to duplicate any code or compile multiple shaders. Arguably, I could always have the shader program for each material be embedded in the material itself, and be auto-generated upon loading the material from the .mtl file. But this still leads to constantly calling glUseProgram, much more than is probably necessary in order to properly render the .obj. There seem to be a number of differing opinions on if it's okay to use hundreds of shaders or if it's best to just use tens of shaders.
      So, ultimately, what is the "right" way to do this? Does using a "master shader" (or a few variants of one) bog down the system compared to using hundreds of shader programs each dedicated to their own corresponding materials? Keeping in mind that the "master shaders" would have to track these additional uniforms and potentially have numerous branches of ifs, it may be possible that the ifs will lead to additional and unnecessary processing. But would that more expensive than constantly calling glUseProgram to switch shaders, or storing the shaders to begin with?
      With all these angles to consider, it's difficult to come to a conclusion. Both possible methods work, and both seem rather convenient for their own reasons, but which is the most performant? Please help this beginner/dummy understand. Thank you!
    • By JJCDeveloper
      I want to make professional java 3d game with server program and database,packet handling for multiplayer and client-server communicating,maps rendering,models,and stuffs Which aspect of java can I learn and where can I learn java Lwjgl OpenGL rendering Like minecraft and world of tanks
    • By AyeRonTarpas
      A friend of mine and I are making a 2D game engine as a learning experience and to hopefully build upon the experience in the long run.

      -What I'm using:
          C++;. Since im learning this language while in college and its one of the popular language to make games with why not.     Visual Studios; Im using a windows so yea.     SDL or GLFW; was thinking about SDL since i do some research on it where it is catching my interest but i hear SDL is a huge package compared to GLFW, so i may do GLFW to start with as learning since i may get overwhelmed with SDL.  
      -Questions
      Knowing what we want in the engine what should our main focus be in terms of learning. File managements, with headers, functions ect. How can i properly manage files with out confusing myself and my friend when sharing code. Alternative to Visual studios: My friend has a mac and cant properly use Vis studios, is there another alternative to it?  
    • By ferreiradaselva
      Both functions are available since 3.0, and I'm currently using `glMapBuffer()`, which works fine.
      But, I was wondering if anyone has experienced advantage in using `glMapBufferRange()`, which allows to specify the range of the mapped buffer. Could this be only a safety measure or does it improve performance?
      Note: I'm not asking about glBufferSubData()/glBufferData. Those two are irrelevant in this case.
    • By xhcao
      Before using void glBindImageTexture(    GLuint unit, GLuint texture, GLint level, GLboolean layered, GLint layer, GLenum access, GLenum format), does need to make sure that texture is completeness. 
  • Popular Now