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CH7 Buffers and Blending. Pixel pipeline Vertex pipeline Course Map Transformation & Lighting...
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Transcript of CH7 Buffers and Blending. Pixel pipeline Vertex pipeline Course Map Transformation & Lighting...
CH7 Buffers and Blending
Pixel pipeline
Vertex pipeline
Course Map
Transformation&
Lighting
Primitiveassembly
Viewport culling&
clipping
Textureblending
Per Fragmentoperations
Bufferoperations
Rasterizersetup
Framebuffer
We are here!
Topics
Blending Fog Accumulation Buffer Stencil Buffer
Blending Example 1/6
#include <math.h>#include <time.h>#include "glut.h"
GLfloat alpha = 0.0;GLfloat pos[4] = {0, 10, 10, 0};GLfloat dif_l[4] = {1.0, 1.0, 1.0, 1.0};GLfloat dif_t[4] = {1.0, 0.5, 0.8, 1.0};GLfloat dif_m[4] = {0.5, 0.8, 0.8, cos(alpha)};
int time1,time2;
void display();void reshape(GLsizei, GLsizei);void idle();
Blending Example 2/6
void main(int argc, char** argv){glutInit(&argc, argv);glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);glutInitWindowSize (500, 500);glutCreateWindow("Blending");glEnable(GL_DEPTH_TEST);glEnable(GL_LIGHTING);glutDisplayFunc(display);glutReshapeFunc(reshape);glutIdleFunc(idle);glutMainLoop();return;
}
Blending Example 3/6
void reshape(GLsizei w, GLsizei h){glViewport(0, 0, 500, 500);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(45, 1 / 1, 0.1, 1000);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(-10, 10, 30, 0, 0, 0, 0, 1, 0);
}void idle(){
time2 = clock();alpha += 3.14 *(time2-time1)/CLK_TCK;dif_m[3] = (cos(alpha) + 1) / 2;time1 = time2;glutPostRedisplay();
}
Blending Example 4/6
void display(){glClearColor(0, 0, 0, 0);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);glEnable(GL_LIGHT0);glLightfv(GL_LIGHT0, GL_POSITION, pos);glLightfv(GL_LIGHT0, GL_DIFFUSE, dif_l);glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, dif_t);glutSolidTeapot(5);
Blending Example 5/6
glEnable(GL_BLEND);glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE, dif_m);glBegin(GL_POLYGON);glNormal3f(0, 0, 1);glVertex3f(-5, -5, 10);glVertex3f(5, -5, 10);glVertex3f(5, 5, 10);glVertex3f(-5, 5, 10);glEnd();glutSwapBuffers();
}
Blending Example 6/6
Blend Function 1/2
glBlendFunc(GLenum sfactor, GLenum dfactor); Color = source_color * sfactor +
destination_color * dfactor
Blend Function 2/2
Parameter (f(R), f(G), f(B), f(A))
GL_ZERO (0,0,0,0)
GL_ONE (1,1,1,1)
GL_SRC_COLOR (RS/kR,GS/kG,BS/kB,AS/kA)
GL_ONE_MINUS_SRC_COLOR (1,1,1,1)-(RS/kR,GS/kG,BS/kB,AS/kA)
GL_DST_COLOR (Rd/kR,Gd/kG,Bd/kB,Ad/kA)
GL_ONE_MINUS_DST_COLOR (1,1,1,1)-(Rd/kR,Gd/kG,Bd/kB,Ad/kA)
GL_SRC_ALPHA AS/kA,AS/kA,AS/kA,AS/kA
GL_ONE_MINUS_SRC_ALPHA (1,1,1,1) -(AS/kA,AS/kA,AS/kA,AS/kA)
GL_DST_ALPHA (AD/kA,AD/kA,AD/kA,AD/kA)
GL_ONE_MINUS_DST_ALPHA (1,1,1,1) -(AD/kA,AD/kA,AD/kA,AD/kA)
How to Use Blending?
Remember to enable glEnable(GL_BLEND);
Set up blend function glBlendFunc(…,…)
Draw object
Fog Example 1/6
#include <gl/glaux.h>#include "glut.h"
GLfloat fcolor[4]={1.0, 1.0, 1.0, 1.0};AUX_RGBImageRec * img;GLuint texObject[1];
void LoadTexture(char* filename){img = auxDIBImageLoad(filename);glGenTextures(1, texObject);glBindTexture(GL_TEXTURE_2D, texObject[0]);glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, img->sizeX, img->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, img->data);glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);
}
Fog Example 2/6
void display(){glEnable(GL_FOG);glFogf(GL_FOG_MODE, GL_EXP);glFogf(GL_FOG_DENSITY, 0.5);glFogfv(GL_FOG_COLOR, fcolor);glClearColor(0, 0, 0, 0);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);glEnable(GL_TEXTURE_2D);glBindTexture(GL_TEXTURE_2D, texObject[0]);
Fog Example 3/6
glBegin(GL_QUADS);glTexCoord2f(0.0, 0.0);glVertex3f(-50.0, 0.0, 0.0);glTexCoord2f(0.0, 100.0);glVertex3f(-50.0, 0.0, 100.0);glTexCoord2f(100.0, 100.0);glVertex3f(50.0, 0.0, 100.0);glTexCoord2f(100.0, 0.0);glVertex3f(50.0, 0.0, 0.0);glEnd();glFlush();glutSwapBuffers();
}
Fog Example 4/6
void reshape(GLsizei w, GLsizei h){glViewport(0, 0, 500, 500);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(45, 1 / 1, 0.1, 1000);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(0.0, 0.5, 0.0, 50.0, 0.0, 50.0, 0.0, 1.0, 0.0);
}
Fog Example 5/6
void main(int argc, char** argv){glutInit(&argc, argv);glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGBA | GLUT_DEPTH);glutInitWindowSize (500, 500);glutCreateWindow("Blending");glEnable(GL_DEPTH_TEST);glEnable(GL_LIGHTING);LoadTexture("check.bmp");glutDisplayFunc(display);glutReshapeFunc(reshape);glutMainLoop();return;
}
Fog Example 6/6
Fog Function 1/2
glFog{f,i}[v]{GLenum pname, param}Pname param
GL_FOG_MODE GL_LINEAR, GL_EXP, GL_EXP2
GL_FOG_DENSITY default : 1.0
GL_FOG_START default : 0.0
GL_FOG_END default : 1.0
GL_FOG_INDEX default : 0.0
GL_FOG_COLOR default : (0,0,0,0)
Fog Function 2/2
GL_LINEAR
GL_EXP
GL_EXP2
COLOR:
How to Use Fog?
Remember to enable glEnable(GL_FOG);
Set up fog function glFogf(…,…)
Draw object
Buffers in OpenGL
Color Buffer Store the color value to be seen on
screen. Depth Buffer
Store the depth values for each pixel. Stencil Buffer Accumulation Buffer
Accumulation Buffer
Screen AccumulationBuffer
+=
return
Accumulation function void glAccum( GLenum op, GLfloat value ); operates on the accumulation buffer. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/opengl/
glfunc01_8o4t.asp op: The accumulation buffer
operation. See next page. value: also see next page.
Accumulation functionop Meaning
GL_ACCUM read each pixel from the color buffer, multiplies the R, G, B, and alpha values by value, then add the result to accumulation buffer.
GL_LOAD the same as GL_ACCUM, but replace the value in accumulation rather than add.
GL_RETURN read values from the accumulation buffer, multiplies them by value, and places the result in the color buffers.
GL_ADD / GL_MULT simply add / multiply the values of each pixel in the accumulation buffer by value, and return to the accumulation buffer. (GL_MULT will clamp value from –1.0 to 1.0 while GL_ADD will not.)
Accumulation example 1/3
#include <GL/glut.h>void GL_display(){
// clear the bufferglClearColor(0.0, 0.0, 0.0, 0.0);glClearAccum(0.0, 0.0, 0.0, 0.0); glClear(GL_ACCUM_BUFFER_BIT);for(int i = 0; i < 360; i++){
glClear(GL_COLOR_BUFFER_BIT);glColor3f(1.0, 1 - (float)i / 180, 1 - (float)i / 360);glPushMatrix();glTranslatef(0, -6, -10);glRotatef(i,0, 1, 0);glutWireTeapot(5);glPopMatrix();glAccum(GL_ACCUM, 0.01);
}glAccum(GL_RETURN, 1.0) ;glutSwapBuffers();
}
Accumulation example 2/3
void GL_reshape(GLsizei w, GLsizei h){
glViewport(0, 0, w, h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(60.0, (GLfloat)w/(GLfloat)h, 1.0, 20.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(0.0, 3.0, 5.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
int main(int argc, char** argv){
glutInit(&argc, argv);glutInitWindowSize(500, 500);glutInitWindowPosition(0, 0);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_ACCUM);glutCreateWindow("Accumulation");glutDisplayFunc(GL_display);glutReshapeFunc(GL_reshape);glutMainLoop();
}
Accumulation example 3/3
Motion blur
Accumulation example 2 1/3
#include <GL/glut.h>
void GL_display(){
glClearColor(0.0, 0.0, 0.0, 0.0);glClearAccum(0.0, 0.0, 0.0, 0.0); glClear(GL_ACCUM_BUFFER_BIT);for(int i = 1; i <5; i++){
glClear(GL_COLOR_BUFFER_BIT);glLoadIdentity();gluLookAt(i * 0.4, 0.0, 8.0, i * 0.4, 0.0, 0.0, 0.0, 1.0, 0.0);glColor3f(1, 0, 0);glutWireTeapot(2);glAccum(GL_ACCUM, (float)i);
}glAccum(GL_RETURN, 0.1) ;glutSwapBuffers();
}
Accumulation example 2 2/3
void GL_reshape(GLsizei w, GLsizei h){
glViewport(0, 0, w, h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(60.0, (GLfloat)w/(GLfloat)h, 1.0, 50.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();
}
int main(int argc, char** argv){
glutInit(&argc, argv);glutInitWindowSize(500, 500);glutInitWindowPosition(0, 0);glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_ACCUM);glutCreateWindow("Accumulation");glutDisplayFunc(GL_display);glutReshapeFunc(GL_reshape);glutMainLoop();
}
Accumulation example 2 3/3
How to use accumulation buffer?
glutInitDisplayMode(GLUT_ACCUM);
glClear(GL_ACCUM_BUFFER_BIT);
Stencil Buffer + Z Buffer
Stencil Buffer + Z Buffer
Z BufferTest
StencilBufferTest
Pixel
Pass
Fail
Screen
Pass Fail
Pass
Stencil Testing 1/2
void glStencilFunc( GLenum func, GLint ref, GLuint mask ); sets the function and reference value
for stencil testing. func: test function, see next page. ref: reference value mask:A mask that is ANDed with both
the reference value and the stored stencil value when the test is done.
Stencil Testing 2/2
param Meaning
GL_NEVER Always fails.
GL_LESS Passes if ( ref & mask) < ( stencil & mask).
GL_LEQUAL Passes if ( ref & mask) ≤ ( stencil & mask).
GL_GEQUAL Passes if ( ref & mask) ≥ ( stencil & mask).
GL_NOTEQUAL Passes if ( ref & mask) ( stencil & mask).
GL_ALWAYS Always passes.
Modify stencil buffer 1/2
void glStencilOp( GLenum fail, GLenum zfail, GLenum zpass ); sets the stencil test actions. fail: The action to take when the
stencil test fails zfail: Stencil action when the stencil
test passes, but the depth test fails. zpass: both the stencil test and the
depth test pass
Modify stencil buffer 2/2
param Meaning
GL_KEEP keep the current value
GL_ZERO set the value in stencil buffer to zero
GL_REPLACE set the value in stencil buffer to ref in glStencilFunc()
GL_INCR increase the current value in stencil buffer
GL_DECR decrease the current value in stencil buffer
GL_INVERT bitwise inverse the current value in stencil buffer
How to use stencil buffer?
1. glutInitDisplayMode(GLUT_STENCIL);
2. glEnable(GL_STENCIL_TEST);
3. glClearStencil(0);4. glClear(GL_STENCIL_BUFFER_BIT);
Stencil buffer example 1/3
#include<gl/glut.h>
void GL_display(){glEnable(GL_DEPTH_TEST);glEnable(GL_STENCIL_TEST);glClearStencil(0);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);glStencilFunc(GL_ALWAYS, 1, 1);glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);glColor3f(0.0, 1.0, 1.0);glutSolidCube(16.0);glClear(GL_DEPTH_BUFFER_BIT);glStencilOp(GL_KEEP, GL_KEEP, GL_INVERT);glStencilFunc(GL_EQUAL, 1, 1);glColor3f(1.0, 1.0, 1.0);glutSolidTeapot(8);glFlush();
}
Stencil buffer example 2/3
void GL_reshape(GLsizei w, GLsizei h){
glViewport(0, 0, w, h);glMatrixMode(GL_PROJECTION);glLoadIdentity();gluPerspective(60.0, (GLfloat)w/(GLfloat)h, 0.5, 100.0);glMatrixMode(GL_MODELVIEW);glLoadIdentity();gluLookAt(0.0, 0.0, 50.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);
}
int main(int argc, char** argv){
glutInit(&argc, argv);glutInitWindowSize(400, 400);glutInitWindowPosition(0, 0);glutInitDisplayMode(GLUT_SINGLE | GLUT_RGBA | GLUT_DEPTH | GLUT_STENCIL);glutCreateWindow("Stencil Buffer");glutDisplayFunc(GL_display);glutReshapeFunc(GL_reshape);glutMainLoop();
}
Stencil buffer example 3/3
Other example… 1/2
void GL_display(){glEnable(GL_DEPTH_TEST);glEnable(GL_STENCIL_TEST);glClearStencil(0);glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT | GL_STENCIL_BUFFER_BIT);glStencilFunc(GL_ALWAYS, 1, 1);glStencilOp(GL_REPLACE, GL_REPLACE, GL_REPLACE);glColor3f(0.0, 1.0, 1.0);glutSolidCube(16.0);glClear(GL_DEPTH_BUFFER_BIT);glStencilOp(GL_KEEP, GL_KEEP, GL_INVERT);glStencilFunc(GL_EQUAL, 1, 1);glColor3f(1.0, 1.0, 1.0);glutSolidTeapot(8);glStencilFunc(GL_NOTEQUAL, 1, 1);glColor3f(1.0, 1.0, 0.0);glPushMatrix();glTranslatef(10, 0, 0);glutSolidSphere(12, 10, 6);glPopMatrix();glFlush();
}
Other example… 2/2
Cooler example…
