Re: texture2D() returning black
Re: texture2D() returning black
- Subject: Re: texture2D() returning black
- From: Patrick Rutkowski <email@hidden>
- Date: Fri, 16 Jul 2010 07:42:07 -0400
- Delivered-to: email@hidden
- Delivered-to: email@hidden
- Dkim-signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:subject:mime-version :content-type:from:in-reply-to:date:cc:content-transfer-encoding :message-id:references:to:x-mailer; bh=IRbyw5cShKfDXuPlZG4VuDA1NGRTxF7N+MeulO7qFKw=; b=Vv/xOeWPnAm0jZGzBxycxi1C0MBlW+Koky4eL2DstI5Llcu6370wAnEt4JjXXonxw1 f4HIil42Z9fD9qiZp66/GJSMFig5HfI0ILeF8vFNl1Gb0xXV0oCwZ+42xjWQMnrdEWMl nzpkxa1SsLkmL3YW2dgstP/KNSy+bvb5ni/fc=
- Domainkey-signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=subject:mime-version:content-type:from:in-reply-to:date:cc :content-transfer-encoding:message-id:references:to:x-mailer; b=ET14drbJlZpVDRh+1WYKEtUemTd+b5eqvGKPplQDssOv1HcEkMK3whXAVc0124HpSS HM89dBzJHjmDknq666xEdprq4SDrnsKDKHcUYHCmpy/oRR3kv9wP9S9rCd8rjZwoi7yM vW06+2gwKNu1Ugi8bMVH1UICI1Z60KT6JjMP8=
I literally _just_ figured that out a few minutes ago. Indeed, I needed a call to:
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
... doh! :-)
My brain didn't register that glTexParameter() still applies in GLSL. I'm still learning which things are purely in the fixed-function realm and which applies to both fixed-function + GLSL.
Thanks for the response nonetheless,
-Patrick
P.S.
Now that that's working though, I'm getting some weird effects around the texture's border. Trying to write it up now.
On Jul 16, 2010, at 7:01 AM, Paul Sargent wrote:
> You may want to set the filtering mode of the texture. By default it's set to a Mipmap mode, and if you don't define all the levels then the colour returned is undefined.
>
> Paul
>
> On 16 Jul 2010, at 10:24, Patrick Rutkowski wrote:
>
>> Ok, so, I'm having a problem here with texture2D(), it's always returning black. Here's what my code does:
>>
>> (1) In my init_renderer() function I set tex_buff to a 10x10 pixel texture filled with pure yellow.
>> (2) I call glGenTextures() to create my tex_id.
>> (3) I call glActiveTexture(GL_TEXTURE0), which might be redundant.
>> (4) I call glBindTexture(GL_TEXTURE_2D, tex_id)
>> (5) I load tex_buff via glTexImage2D()
>> (6) I call glGetUniformLocation() to get the sampler's location from the shader program, and then I print the location to verify that it's not -1.
>> (7) I call glUseProgram(program)
>> (8) I call glUniform1i(glsl_texture, 0), which if I understand correctly tells that sampler to use GL_TEXTURE0.
>> (9) During render() I then once again call glActiveTexture() and glBindTexture(), which is probably redundant, but why not.
>> (10) I then render the square, and it comes up black.
>>
>> In the fragment shader, if I delete:
>>
>> gl_FragColor = texture2D(texture, frag_pos.xy)
>> ... and instead replace it with:
>> gl_FragColor = vec4(<foo>, <bar>, <baz>, 1.0);
>> ... then the square does indeed show color (foo, bar, baz).
>>
>> I'm just really confused here, think anyone might be able to have a look? The code is pasted below, it's a self contained file. If you build it on any UNIX system, it should run:
>>
>> ==============================================
>>
>> #include <X11/Xlib.h>
>> #include <GL/gl.h>
>> #include <GL/glext.h>
>> #include <GL/glx.h>
>> #include <stdarg.h>
>> #include <stdio.h>
>> #include <stdlib.h>
>>
>> Display* dpy;
>> Window win;
>> GLXContext ctx;
>>
>> GLuint vertex_shader;
>> GLuint fragment_shader;
>> GLuint program;
>>
>> #define TEX_WIDTH 10
>> #define TEX_HEIGHT 10
>>
>> GLint glsl_texture;
>> GLuint tex_id;
>> GLubyte tex_buff[4 * TEX_WIDTH * TEX_HEIGHT];
>>
>> const char* vertex_shader_source =
>> "\n" "varying vec2 frag_pos;"
>> "\n" ""
>> "\n" "void"
>> "\n" "main(void)"
>> "\n" "{"
>> "\n" " gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;"
>> "\n" " frag_pos = gl_Position.xy;"
>> "\n" "}"
>> "\n"
>> ;
>>
>> const char* fragment_shader_source =
>> "\n" "varying vec2 frag_pos;"
>> "\n" "uniform sampler2D texture;"
>> "\n" ""
>> "\n" "void"
>> "\n" "main(void)"
>> "\n" "{"
>> "\n" " gl_FragColor = texture2D(texture, frag_pos.xy);"
>> "\n" "}"
>> "\n"
>> ;
>>
>> void
>> die(const char* fmt, ...)
>> {
>> va_list ap;
>> va_start(ap, fmt);
>> vprintf(fmt, ap);
>> va_end(ap);
>> printf("\n");
>> exit(1);
>> }
>>
>> GLuint
>> load_shader(GLenum type, const char* source)
>> {
>> GLint success;
>> GLuint shader;
>>
>> /* Add source */
>> shader = glCreateShader(type);
>> glShaderSource(shader, 1, &source, NULL);
>>
>> /* Compile & report errors */
>> glCompileShader(shader);
>> glGetShaderiv(shader, GL_COMPILE_STATUS, &success);
>> if( ! success )
>> {
>> char* log;
>> GLint log_size;
>> glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &log_size);
>> log = malloc(log_size);
>> glGetShaderInfoLog(shader, log_size, NULL, log);
>> die("ERROR: shader failed to compile:\n%s", log);
>> }
>>
>> return shader;
>> }
>>
>> GLuint
>> link_program(GLuint first, ...)
>> {
>> GLint success;
>> GLuint program;
>> GLuint shader;
>> va_list ap;
>>
>> program = glCreateProgram();
>>
>> /* Attach all shaders */
>> va_start(ap, first);
>> for(shader = first; shader != 0; shader = va_arg(ap, GLuint))
>> glAttachShader(program, shader);
>> va_end(ap);
>>
>> /* Link & report errors */
>> glLinkProgram(program);
>> glGetProgramiv(program, GL_LINK_STATUS, &success);
>> if( ! success )
>> {
>> char* log;
>> GLint log_size;
>> glGetProgramiv(program, GL_INFO_LOG_LENGTH, &log_size);
>> log = malloc(log_size);
>> glGetProgramInfoLog(program, log_size, NULL, log);
>> die("ERROR: program failed to link:\n%s", log);
>> }
>>
>> /* Validate */
>> glValidateProgram(program);
>> glGetProgramiv(program, GL_VALIDATE_STATUS, &success);
>> if( ! success )
>> {
>> char* log;
>> GLint log_size;
>> glGetProgramiv(program, GL_INFO_LOG_LENGTH, &log_size);
>> log = malloc(log_size);
>> glGetProgramInfoLog(program, log_size, NULL, log);
>> die("ERROR: program failed to validate:\n%s", log);
>> }
>>
>> return program;
>> }
>>
>> void
>> init_renderer(void)
>> {
>> size_t x, y;
>>
>> /* Compile Shaders */
>>
>> vertex_shader =
>> load_shader(GL_VERTEX_SHADER, vertex_shader_source);
>>
>> fragment_shader =
>> load_shader(GL_FRAGMENT_SHADER, fragment_shader_source);
>>
>> /* Link Program */
>>
>> program = link_program(vertex_shader, fragment_shader, 0);
>>
>> /* Generic GL Initialization */
>>
>> glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
>>
>> for(y = 0; y < TEX_HEIGHT; y++)
>> {
>> for(x = 0; x < TEX_WIDTH; x++)
>> {
>> GLubyte* pixel = &tex_buff[x*4 + (4 * y * TEX_WIDTH)];
>> pixel[0] = 255;
>> pixel[1] = 255;
>> pixel[2] = 0;
>> pixel[3] = 255;
>> }
>> }
>>
>> glActiveTexture(GL_TEXTURE0);
>>
>> glGenTextures(1, &tex_id);
>> glBindTexture(GL_TEXTURE_2D, tex_id);
>>
>> glTexImage2D
>> (
>> GL_TEXTURE_2D,
>> 0,
>> GL_RGBA,
>> TEX_WIDTH,
>> TEX_HEIGHT,
>> 0,
>> GL_RGBA,
>> GL_UNSIGNED_BYTE,
>> &tex_buff[0]
>> );
>>
>> glsl_texture = glGetUniformLocation(program, "texture");
>> printf(
>> "glGetUniformLocation(program, \"texture\"): %d\n", glsl_texture
>> );
>>
>> glUseProgram(program);
>> glUniform1i(glsl_texture, 0);
>> }
>>
>> void
>> render(void)
>> {
>> glClear(GL_COLOR_BUFFER_BIT);
>>
>> glUseProgram(program);
>>
>> glActiveTexture(GL_TEXTURE0);
>> glBindTexture(GL_TEXTURE_2D, tex_id);
>>
>> glBegin(GL_POLYGON);
>> glVertex2f(-1.0f, -1.0f);
>> glVertex2f(+1.0f, -1.0f);
>> glVertex2f(+1.0f, +1.0f);
>> glVertex2f(-1.0f, +1.0f);
>> glEnd();
>> }
>>
>> void
>> event_loop(void)
>> {
>> XEvent e;
>>
>> while(1)
>> {
>> if( XCheckMaskEvent(dpy, ~0L, &e) )
>> {
>> printf("xevent!\n");
>> }
>>
>> render();
>> glXSwapBuffers(dpy, win);
>> }
>> }
>>
>> void
>> create_window(void)
>> {
>> XSetWindowAttributes win_attrs;
>> unsigned long attrs_mask = CWColormap | CWEventMask;
>>
>> int attrs[] =
>> {
>> GLX_DOUBLEBUFFER,
>> GLX_RGBA,
>> GLX_RED_SIZE, 8,
>> GLX_GREEN_SIZE, 8,
>> GLX_BLUE_SIZE, 8,
>> None
>> };
>>
>> XVisualInfo* vi = glXChooseVisual
>> (
>> dpy,
>> DefaultScreen(dpy),
>> attrs
>> );
>>
>> if( vi == NULL )
>> die("glXChooseVisual() failed");
>>
>> win_attrs.event_mask = KeyPressMask | PointerMotionMask;
>>
>> win_attrs.colormap = XCreateColormap
>> (
>> dpy,
>> RootWindow(dpy, vi->screen),
>> vi->visual,
>> AllocNone
>> );
>>
>> win = XCreateWindow
>> (
>> dpy,
>> DefaultRootWindow(dpy),
>> 200, /* x */
>> 200, /* y */
>> 500, /* width */
>> 500, /* height */
>> 0, /* border */
>> vi->depth, /* depth */
>> InputOutput, /* class */
>> vi->visual, /* visual */
>> attrs_mask, /* win_attrs mask */
>> &win_attrs /* win_attrs */
>> );
>>
>> ctx = glXCreateContext(dpy, vi, NULL, True);
>> glXMakeCurrent(dpy, win, ctx);
>>
>> XMapWindow(dpy, win);
>> }
>>
>> int
>> main(void)
>> {
>> dpy = XOpenDisplay(NULL);
>> if( dpy == NULL )
>> die("XOpenDisplay(NULL) failed");
>>
>> create_window();
>> init_renderer();
>> event_loop();
>>
>> return 0;
>> }
>>
>> _______________________________________________
>> Do not post admin requests to the list. They will be ignored.
>> Mac-opengl mailing list (email@hidden)
>> Help/Unsubscribe/Update your Subscription:
>>
>> This email sent to email@hidden
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Mac-opengl mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden
Visit the Apple Store online or at retail locations.
1-800-MY-APPLE
Contact Apple | Terms of Use | Privacy Policy
Copyright © 2011 Apple Inc. All rights reserved.
