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POGL & GLSL: Bump Mapping: What's wrong with this textbook example?
 

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  1. POGL & GLSL: Bump Mapping: What's wrong with this textbook example?
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    <p><strong>Here's what the README says this example does:</strong> "bump map on one polygon with a rotation light". Let me add: the polygon is a square, and the bump map on it should produce a raised-looking square within the original polygon square. The values for i and j (pixel iteration) in the second 'for' loop in main() are indicative of this inner square pattern. </p> <p><strong>Problem</strong>: When I run it, the display window comes up but it's blank white. Maybe you can try running it yourself: if it works, let's find differences in our setup; if it, doesn't please help find what's wrong with the code. The code is here: <a href="http://www.cs.unm.edu/~angel/BOOK/INTERACTIVE_COMPUTER_GRAPHICS/SIXTH_EDITION/" rel="nofollow">http://www.cs.unm.edu/~angel/BOOK/INTERACTIVE_COMPUTER_GRAPHICS/SIXTH_EDITION/</a>. Click on "Code", then "CHAPTER07/". It's example 7.3. Also, below is the code for reference. Note: I added "#version 150" to fshader73.glsl to get rid of a version error at runtime.</p> <p><strong>example3.cpp</strong>:</p> <pre><code>/* sets up flat mesh */ /* sets up elapsed time parameter for use by shaders */ #include "Angel.h" #define N 256 GLfloat normals[N][N][3]; GLuint program; GLuint texMapLocation; GLfloat tangent[3] = {1.0, 0.0, 0.0}; typedef Angel::vec4 point4; typedef Angel::vec4 color4; point4 points[6]; vec2 tex_coord[6]; mat4 ctm, projection; vec4 normal = point4(0.0, 1.0, 0.0, 0.0); color4 light_diffuse = color4(1.0, 1.0, 1.0, 1.0); color4 material_diffuse = color4(0.7, 0.7, 0.7, 1.0); point4 light_position = point4(0.0, 10.0, 0.0, 1.0); vec4 eye = vec4(2.0, 2.0, 2.0, 1.0); vec4 at = vec4(0.5, 0.0, 0.5, 1.0); vec4 up = vec4(0.0, 1.0, 0.0, 1.0); GLuint loc, loc2; GLuint buffers[2]; GLuint normal_loc; GLuint diffuse_product_loc; GLuint light_position_loc; GLuint ctm_loc, projection_loc; GLuint tangent_loc; /* standard OpenGL initialization */ vec4 product(vec4 a, vec4 b) { return vec4(a[0]*b[0], a[1]*b[1], a[2]*b[2], a[3]*b[3]); } static void init() { const float meshColor[] = {0.7f, 0.7f, 0.7f, 1.0f}; glMaterialfv(GL_FRONT, GL_AMBIENT_AND_DIFFUSE, meshColor); glClearColor(1.0f, 1.0f, 1.0f, 1.0f); glBindTexture(GL_TEXTURE_2D, 0); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, N, N, 0, GL_RGB, GL_FLOAT, normals); glEnable(GL_TEXTURE_2D); glEnable(GL_DEPTH_TEST); loc = glGetAttribLocation(program, "vPosition"); glEnableVertexAttribArray(loc); glVertexAttribPointer(loc, 4, GL_FLOAT, GL_FALSE, 0, points); loc2 = glGetAttribLocation(program, "texcoord"); glEnableVertexAttribArray(loc2); glVertexAttribPointer(loc2, 2, GL_FLOAT, GL_FALSE, 0, tex_coord); glGenBuffers(2, buffers); glBindBuffer(GL_ARRAY_BUFFER, buffers[0]); glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW); tangent_loc = glGetUniformLocation(program, "objTangent"); glUniform3fv(tangent_loc, 3, tangent); normal_loc = glGetUniformLocation(program, "Normal"); glUniform4fv(normal_loc, 4, normal); vec4 diffuse_product = product(light_diffuse, material_diffuse); diffuse_product_loc = glGetUniformLocation(program, "DiffuseProduct"); glUniform4fv(diffuse_product_loc, 4, diffuse_product); light_position_loc = glGetUniformLocation(program, "LightPosition"); glUniform4fv(light_position_loc, 4, light_position); ctm_loc = glGetUniformLocation(program, "ModelView"); ctm = LookAt(eye, at , up); glUniformMatrix4fv(ctm_loc, 16, GL_TRUE, ctm); mat4 nm; GLfloat det; det = ctm[0][0]*ctm[1][1]*ctm[2][2]+ctm[0][1]*ctm[1][2]*ctm[2][1] -ctm[2][0]*ctm[1][1]*ctm[0][2]-ctm[1][0]*ctm[0][1]*ctm[2][2]-ctm[0][0]*ctm[1][2]*ctm[2][1]; nm[0][0] = (ctm[1][1]*ctm[2][2]-ctm[1][2]*ctm[2][1])/det; nm[0][1] = -(ctm[0][1]*ctm[2][2]-ctm[0][2]*ctm[2][1])/det; nm[0][2] = (ctm[0][1]*ctm[2][0]-ctm[2][1]*ctm[2][2])/det; nm[1][0] = -(ctm[0][1]*ctm[2][2]-ctm[0][2]*ctm[2][1])/det; nm[1][1] = (ctm[0][0]*ctm[2][2]-ctm[0][2]*ctm[2][0])/det; nm[1][2] = -(ctm[0][0]*ctm[2][1]-ctm[2][0]*ctm[0][1])/det; nm[2][0] = (ctm[0][1]*ctm[1][2]-ctm[1][1]*ctm[0][2])/det; nm[2][1] = -(ctm[0][0]*ctm[1][2]-ctm[0][2]*ctm[1][0])/det; nm[2][2] = (ctm[0][0]*ctm[1][1]-ctm[1][0]*ctm[0][1])/det; GLuint nm_loc; nm_loc = glGetUniformLocation(program, "NormalMatrix"); glUniformMatrix4fv(nm_loc, 16, GL_TRUE, nm); projection_loc = glGetUniformLocation(program, "Projection"); projection = Ortho(-0.75,0.75,-0.75,0.75,-5.5,5.5); glUniformMatrix4fv(projection_loc, 16, GL_TRUE, projection); texMapLocation = glGetUniformLocation(program, "texMap"); } /* set up uniform parameter */ void mesh() { point4 vertices[4] = {point4(0.0, 0.0, 0.0, 1.0), point4(1.0, 0.0, 0.0, 1.0), point4(1.0, 0.0, 1.0, 1.0), point4(0.0, 0.0, 1.0, 1.0)}; points[0] = vertices[0]; tex_coord[0] = vec2(0.0, 0.0); points[1] = vertices[1]; tex_coord[1] = vec2(1.0, 0.0); points[2] = vertices[2]; tex_coord[2] = vec2(1.0, 1.0); points[3] = vertices[2]; tex_coord[3] = vec2(1.0, 1.0); points[4] = vertices[3]; tex_coord[4] = vec2(0.0, 1.0); points[5] = vertices[0]; tex_coord[5] = vec2(0.0, 0.0); } static void draw() { glUniform1i(texMapLocation, 0); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); mesh(); glDrawArrays(GL_TRIANGLES, 0, 6); glutSwapBuffers(); } static void reshape(int w, int h) { glViewport(0, 0, w, h); glutPostRedisplay(); } static void keyboard(unsigned char key, int x, int y) { switch (key) { case 27: case 'Q': case 'q': exit(EXIT_SUCCESS); } } void idle() { int t; t = glutGet(GLUT_ELAPSED_TIME); light_position[0] = 5.5*sin(0.001*t); light_position[2] = 5.5*cos(0.001*t); glUniform4fv(light_position_loc, 4, light_position); glutPostRedisplay(); } int main(int argc, char** argv) { int i,j, k; float d; float data[N+1][N+1]; for(i=0;i&lt;N+1;i++) for(j=0;j&lt;N+1;j++) data[i][j]=0.0; for(i=N/4; i&lt; 3*N/4; i++) for(j=N/4;j&lt;3*N/4;j++) data[i][j] = 1.0; for(i=0;i&lt;N;i++) for(j=0;j&lt;N;j++) { normals[i][j][0] = data[i][j]-data[i+1][j]; normals[i][j][2] = data[i][j]-data[i][j+1]; normals[i][j][1]= 1.0; } for(i=0;i&lt;N;i++) for(j=0;j&lt;N;j++) { d = 0.0; for(k=0;k&lt;3;k++) d+=normals[i][j][k]*normals[i][j][k]; d=sqrt(d); for(k=0;k&lt;3;k++) normals[i][j][k]= 0.5*normals[i][j][k]/d+0.5; } glutInit(&amp;argc, argv); glutInitDisplayMode(GLUT_RGBA | GLUT_DOUBLE | GLUT_DEPTH); glutInitWindowSize(1024, 1024); glutInitContextVersion( 3, 2 ); glutInitContextProfile( GLUT_CORE_PROFILE ); glutCreateWindow("Simple GLSL example"); glutDisplayFunc(draw); glutReshapeFunc(reshape); glutKeyboardFunc(keyboard); glutIdleFunc(idle); glewInit(); program = InitShader("vshader73.glsl", "fshader73.glsl"); init(); glutMainLoop(); return 0; } </code></pre> <p><strong>vshader73.glsl</strong>:</p> <pre><code>/* bump map vertex shader */ #version 150 out vec3 L; /* light vector in texture-space coordinates */ out vec3 V; /* view vector in texture-space coordinates */ in vec2 texcoord; in vec4 vPosition; uniform vec4 Normal; uniform vec4 LightPosition; uniform mat4 ModelView; uniform mat4 Projection; uniform mat4 NormalMatrix; uniform vec3 objTangent; /* tangent vector in object coordinates */ out vec2 st; void main() { mat3 NM3; NM3[0][0] = NormalMatrix[0][0]; NM3[0][1] = NormalMatrix[0][1]; NM3[0][2] = NormalMatrix[0][2]; NM3[1][0] = NormalMatrix[1][0]; NM3[1][1] = NormalMatrix[1][1]; NM3[1][2] = NormalMatrix[1][2]; NM3[2][0] = NormalMatrix[2][0]; NM3[2][1] = NormalMatrix[2][1]; NM3[2][2] = NormalMatrix[2][2]; gl_Position = Projection*ModelView*vPosition; st = texcoord; vec3 eyePosition = vec3(ModelView*vPosition); vec3 eyeLightPos = LightPosition.xyz; /* normal, tangent and binormal in eye coordinates */ vec3 N = normalize(NM3*Normal.xyz); vec3 T = normalize(NM3*objTangent); vec3 B = cross(N, T); /* light vector in texture space */ L.x = dot(T, eyeLightPos-eyePosition); L.y = dot(B, eyeLightPos-eyePosition); L.z = dot(N, eyeLightPos-eyePosition); L = normalize(L); /* view vector in texture space */ V.x = dot(T, -eyePosition); V.y = dot(B, -eyePosition); V.z = dot(N, -eyePosition); V = normalize(V); } </code></pre> <p><strong>fshader73.glsl</strong>:</p> <pre><code>#version 150 in vec3 L; in vec3 V; uniform sampler2D texMap; in vec2 st; uniform vec4 DiffuseProduct; out vec4 fColor; void main() { vec4 N = texture2D(texMap, st); vec3 NN = normalize(2.0*N.xyz-1.0); vec3 LL = normalize(L); float Kd = max(dot(NN.xyz, LL), 0.0); fColor = Kd*DiffuseProduct; } </code></pre> <p><strong>EDIT</strong>:</p> <p>Following Brett's comment, I replaced <code>glBindTexture(GL_TEXTURE_2D, 0)</code> with the below -- still getting a blank white window:</p> <pre><code>GLuint texture; glGenTextures( 1, &amp;texture ); glBindTexture(GL_TEXTURE_2D, texture); ... glActiveTexture(GL_TEXTURE0); </code></pre>
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    1. USRooster
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    1. This table or related slice is empty.
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    1. COYou can't use the texture binding `(0)`, it's reserved for the 'default' texture - see: `glGenTextures`.
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      1. POGL & GLSL: Bump Mapping: What's wrong with this textbook example?
      1. USBrett Hale
    2. COAh so perhaps there is no texture to be bound, because the default texture has not been set? I'm going to ditch the 0 and use `glGenTextures` to put my own texture into the binding. Any idea how the author intended this example to work?
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      1. POGL & GLSL: Bump Mapping: What's wrong with this textbook example?
      1. USRooster
    3. COIn the meantime, please anyone, I'm not really convinced that glBindTexture(GL_TEXTURE_2D, 0) is incorrect. An explanation of what the default texture is in this case, why it is incorrect, and the proper way to use "default texture" would help.
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      1. POGL & GLSL: Bump Mapping: What's wrong with this textbook example?
      1. USRooster
 

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