GLSL中的多个纹理 - 只有一个有效

Question

我的问题是在GLSL着色器中可以访问多个纹理.这是我正在做的事情:

着色器:

uniform sampler2D sampler0;
uniform sampler2D sampler1;
uniform float blend;
void main( void )
{
    vec2 coords = gl_TexCoord[0];
    vec4 col = texture2D(sampler0, coords);
    vec4 col2 = texture2D(sampler1, coords);
    if (blend > 0.5){
        gl_FragColor = col;
    } else {
        gl_FragColor = col2;
    }
};

因此,我只需根据统一变量在两个颜色值之间进行选择.足够简单(这是一个测试),但是当混合<= 0.5时,我得到全黑,而不是预期的行为.

OpenGL代码:

m_sampler0location = m_shader.FindUniform("sampler0");
m_sampler1location = m_shader.FindUniform("sampler1");
m_blendlocation = m_shader.FindUniform("blend");

glActiveTexture(GL_TEXTURE0);
glEnable(GL_TEXTURE_2D);
m_extensions.glUniform1iARB(m_sampler0location, 0);
glBindTexture(GL_TEXTURE_2D, Texture0.Handle);  
glActiveTexture(GL_TEXTURE1);
glEnable(GL_TEXTURE_2D);
m_extensions.glUniform1iARB(m_sampler1location, 1);
glBindTexture(GL_TEXTURE_2D, Texture1.Handle);
glBegin(GL_QUADS);
    //lower left
    glTexCoord2f(0, 0);
    glVertex2f(-1.0, -1.0);
    //upper left
    glTexCoord2f(0, maxCoords0.t);
    glVertex2f(-1.0, 1.0);
    //upper right
    glTexCoord2f(maxCoords0.s, maxCoords0.t);
    glVertex2f(1.0, 1.0);
    //lower right
    glTexCoord2f(maxCoords0.s, 0);
    glVertex2f(1.0, -1.0);
glEnd()

着色器在所有这些之前被编译和绑定.在该过程中的所有健全性检查表明它没有问题. 正如我所说,col着色器程序中的值反映了纹理中的碎片; 价值col2是黑色的.显示的纹理是最后一个活动纹理 - 如果我将最后一个更改glBindTexture为绑定Texture0.Handle,纹理会更改.根据Bahbar的回复修复.

事实上,即使我添加了像gl_FragColor.r = blend;着色器的最后一行一样的东西,场景渲染全黑.但是,如果我注释掉调用glActiveTexture(GL_TEXTURE1);,则着色器再次起作用,并且sampler0和sampler1中都会出现相同的纹理.

这是怎么回事？这条线glActiveTexture(GL_TEXTURE1);似乎工作得很好,后来证明了这一点glGetIntegerv(GL_ACTIVE_TEXTURE, &anint).为什么它如此可怕地打破一切？我已经尝试升级我的显示驱动程序了.

Answer 1

这是一个基本的GLUT示例(在OS X上编写,根据需要进行调整),生成两个棋盘格纹,使用两个采样器加载着色器,并通过对每个(一个红色,一个蓝色)和混合进行着色来组合它们.看看这是否适合您:

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

#include <GLUT/glut.h>
#include <OpenGL/gl.h>
#include <OpenGL/glu.h>

#define kTextureDim 64

GLuint t1;
GLuint t2;

/* adapted from the red book */
GLuint makeCheckTex() {
    GLubyte image[kTextureDim][kTextureDim][4]; // RGBA storage

    for (int i = 0; i < kTextureDim; i++) {
        for (int j = 0; j < kTextureDim; j++) {
            int c = ((((i & 0x8) == 0) ^ ((j & 0x8)) == 0))*255;
            image[i][j][0]  = (GLubyte)c;
            image[i][j][1]  = (GLubyte)c;
            image[i][j][2]  = (GLubyte)c;
            image[i][j][3]  = (GLubyte)255;
        }
    }

    GLuint texName;
    glGenTextures(1, &texName);    
    glBindTexture(GL_TEXTURE_2D, texName);
    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);
    glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, kTextureDim, kTextureDim, 0, GL_RGBA, GL_UNSIGNED_BYTE, image);

    return texName;
}

void loadShader() {
#define STRINGIFY(A) #A

    const GLchar* source = STRINGIFY(

                                     uniform sampler2D tex1;
                                     uniform sampler2D tex2;

                                     void main() {
                                         vec4 s1 = texture2D(tex1, gl_TexCoord[0].st);
                                         vec4 s2 = texture2D(tex2, gl_TexCoord[0].st + vec2(0.0625, 0.0625));
                                         gl_FragColor = mix(vec4(1, s1.g, s1.b, 0.5), vec4(s2.r, s2.g, 1, 0.5), 0.5);
                                     }

                                     );

    GLuint program = glCreateProgram();
    GLuint shader = glCreateShader(GL_FRAGMENT_SHADER);
    glShaderSource(shader, 1, &source, NULL);
    glCompileShader(shader);

    GLint logLength;
    glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &logLength);
    if (logLength > 0) {
        GLchar* log = (GLchar*)malloc(logLength);
        glGetShaderInfoLog(shader, logLength, &logLength, log);
        printf("Shader compile log:\n%s\n", log);
        free(log);
    }

    glAttachShader(program, shader);  
    glLinkProgram(program);

    glGetProgramiv(program, GL_INFO_LOG_LENGTH, &logLength);
    if (logLength > 0) {
        GLchar* log = (GLchar*)malloc(logLength);
        glGetProgramInfoLog(program, logLength, &logLength, log);
        printf("Program link log:\n%s\n", log);
        free(log);
    }

    GLuint t1Location = glGetUniformLocation(program, "tex1");
    GLuint t2Location = glGetUniformLocation(program, "tex2");

    glUniform1i(t1Location, 0);
    glUniform1i(t2Location, 1);

    glUseProgram(program);
}


void init()
{
    glClearColor(0.0, 0.0, 0.0, 0.0);
    glEnable(GL_DEPTH_TEST);
    glShadeModel(GL_FLAT);

    t1 = makeCheckTex();
    t2 = makeCheckTex();

    loadShader();
}


void display()
{
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    glLoadIdentity();

    glActiveTexture(GL_TEXTURE0);
    glEnable(GL_TEXTURE_2D);
    glBindTexture(GL_TEXTURE_2D, t1);

    glActiveTexture(GL_TEXTURE1);
    glBindTexture(GL_TEXTURE_2D, t2);

    glBegin(GL_QUADS);
    //lower left
    glTexCoord2f(0, 0);
    glVertex2f(-1.0, -1.0);
    //upper left
    glTexCoord2f(0, 1.0);
    glVertex2f(-1.0, 1.0);
    //upper right
    glTexCoord2f(1.0, 1.0);
    glVertex2f(1.0, 1.0);
    //lower right
    glTexCoord2f(1.0, 0);
    glVertex2f(1.0, -1.0);
    glEnd();

    glutSwapBuffers();
}


void reshape(int w, int h)
{
    glViewport(0, 0, w, h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(-2, 2, -2, 2, -2, 2);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}


int main(int argc, char **argv)
{
    glutInit(&argc, argv);

    glutInitDisplayMode(GLUT_DOUBLE | GLUT_DEPTH | GLUT_RGBA);

    glutInitWindowSize(512, 512);
    glutInitWindowPosition(0, 0);

    glutCreateWindow("GLSL Texture Blending");

    glutReshapeFunc(reshape);
    glutDisplayFunc(display);
    glutIdleFunc(display);

    init();

    glutMainLoop();
    return 0;
}

希望结果看起来像这样(你可以注释掉glUseProgram调用以查看没有着色器绘制的第一个纹理):

Answer 2

只是为了帮助其他可能对使用多种纹理感兴趣的人,并且在寻找答案的几天之后会感到绝望.我发现你需要打电话

glUseProgram(program);

GLuint t1Location = glGetUniformLocation(program, "tex1");
GLuint t2Location = glGetUniformLocation(program, "tex2");

glUniform1i(t1Location, 0);
glUniform1i(t2Location, 1);

按顺序工作(glUseProgram是我在网上找到的99%示例代码的最后一条指令).现在可能只是我的情况而不影响地球上的其他任何人,但以防万一我以为我会分享.

Answer 3

很晚才回复,但对于任何遇到这种情况的人 - 我遇到了同样的问题,经过短暂的摆弄,我意识到调用glActiveTexture(GL_TEXTURE0)修复了这个问题.如果活动纹理单元没有"重置"为零,那么看起来有点困惑.这可能是系统依赖的行为; 我用Mesa 8.0.4运行64位Archlinux.