OpenGL Programming Guide (Red Book) State Management and Drawing Geometric Objects 고려대학교 그래픽스 연구실 강 신 진

Goal  Clear the window to an arbitrary color  Force any pending drawing to complete  Draw with any geometric primitive  Turn states on and off any query states variables  Control the display of geometric primitives  Specify normal vectors at appropriate points

Contents  A Drawing Survival Kit  Describing Points, Lines, and Polygons  Basic State Management  Display Points, Lines, and Polygons  Normal Vectors

A Drawing Survival Kit

Clearing Window BufferName Color bufferGL_COLOR_BUFFER_BIT Depth bufferGL_DEPTH_BUFFER_BIT Accumulation bufferGL_ACCUM_BUFFER_BIT Stencil bufferGL_STENCIL_BUFFER_BIT glClearColor(0.0f, 0.0f, 0.0f, 0.0f); glClear(GL_CLEAR_BUFFER_BIT); Lesson27\Lesson 27.exe

Specifying a Color  Description of the shape of an object Independent of the description of its color  Order of Programming Setting the color or coloring scheme Drawing the objects  To set a color glColor3f(1.0f, 1.0f, 1.0f); //black glColor3f(0.0f, 1.0f, 1.0f); //cyan

Forcing Completion of Drawing Void glFlush(void); Forces previously issued OpenGL commands to begin execution, thus guaranteeing that they complete in finite time Void glFinish(void); Forces all previously issued OpenGL commands to complete. The command doesn’t return until all effects from previous commands are fully realized.

Coordinate System Survival Kit glutReshapeFunc(reshape) Void reshape(int w, int h) { glViewport(0, 0, (GLsizei) w, (GLsizei) h); glMatrixMode(GL_PROJECTION); glLoadIdentity(); gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f); }

Describing Points, Lines, and Polygons 점선폴리곤 \lesson1.exe

What are Points, Lines and Polygons?  Differences between mathematician and OpenGL 1.Difference from the limitations of computer-based calculations.  Floating-point calculations are of finite precision, and they have round-off errors 2. Difference from the limitations of a graphics display  The smallest displayable unit is a pixel, and pixel is not infinitely small

Specifying Vertices glVertex2s(2, 3); glVertex3d(0.0, 0.0, ); glVertex4f(2.3, 1.0, -2.2, 2.0); glDouble dvect[3] = {5.0, 9.0, }; glVertex3dv(dvect); glVertex() type glVertex*() type Between glBegin() and glEnd()

OpenGL Geometric Drawing Primitives Void glBegin(GLenum mode); glBegin 모드 \Debug\lesson1.exe

Restriction on Using glBegin() and glEnd() glVertex*()Set vertex coordinates glColor*()Set current color glIndex*()Set current color index glNormal*()Set normal vector coordinates glTexCoord*()Set texture coordinates glMultiTexCoord*ARB()Set texture coordinates for multitexturing glEdgeFlag*()Control drawing of edges glMaterial*()Set material properties glArrayElement()Extract vertex array data glEvalCoord*(), ~Point*()Generate coordinates glCallList(), glCallLists()Execute display list(s)

Basic State Management

Method Void glEnable(GLenum cap); Void glDisable(GLenum cap); Checking & Debugging method GLboolean glIsEnabled(GLenum capability); Capability Example GL_BLEND, GL_DEPTH_TEST, GL_LINE_STIPPLE, GL_LIGHTING etc.

Display Points, Lines, and Polygons

Point Detail Controlling size of a rendered point Void glPointSize(GLfloat size); Whether antialiasing is enabled or disabled Disabledwidths are rounded to integer widths Enablednoninteger widths aren ’ t rounded, variation of intensity Antilaliasing\Debug\Antilaliasing.exe

Line Details Controlling width of a rendered line Void glLineWidth(GLfloat size); Stippled Lines glLineStipple(1, 0x3F07); glEnable(GL_LINE_STIPPLE);

Polygon Details - 1 Polygons as Points, Outlines or Solids Void glPolygonMode(GLenum face, GLenum mode); glPolygonMode(GL_FRONT, GL_FILL); glPolygonMode(GL_BACK, GL_LINE); glPolygonMode(GL_FRONT_AND_BACK, GL_POINT); Reserving and Culling Polygon Faces Void glFrontFace(GLenum mode); //GL_CW, GL_CCW glBegin 모드 \Debug\lesson1.exe

Polygon Details - 2 Void glCullFace(GLenum mode); modeGL_FRONT, GL_BACK, GL_FRONT_AND_BACK Stippling Polygons glEnable(GL_POLYGON_STIPPLE); Void glPolygonStipple(const GLubyte *mask); Boundary Edges Void glEdgeFlags(GLboolean flag); Void glEdgeFlagv(const GLboolean *flag);

Normal Vectors

Normal Vector A normal vector is a vector that points in a direction that ’ s perpendicular to surface OpenGL Method Void glNormal3{bsidf}(TYPE nx, TYPE ny, TYPE nz); Void glNormal3{bsidf}v(const TYPE *v); Normalization glEnable(GL_NORMALIZE);