my GL notes

7/28/2019 my GL notes

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glutInit

glutInit is used to initialize the GLUT library.

Usage

void glutInit(int *argcp, char **argv);

argcpA pointer to the program's unmodifiedargc variable from main.

argvThe program's unmodifiedargv variable from main.

Description

glutInit will initialize the GLUT library and negotiate a session with the windowsystem.


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glutInitDisplayMode

glutInitDisplayMode sets the initial display mode.

Usage

void glutInitDisplayMode(unsigned int mode);mode

Display mode, normally the bitwise OR-ing of GLUT display mode bitmasks. See values below:

GLUT_RGBABit mask to select an RGBA mode window. This is the default if

neitherGLUT_RGBA norGLUT_INDEX are specified.GLUT_RGB

An alias forGLUT_RGBA.

GLUT_INDEXBit mask to select a color index mode window. This overrides GLUT_RGBA if itis also specified.

GLUT_SINGLEBit mask to select a single buffered window. This is the default if

neitherGLUT_DOUBLE orGLUT_SINGLE are specified.GLUT_DOUBLE

Bit mask to select a double buffered window. This overrides GLUT_SINGLE if

it is also specified.GLUT_DEPTH

Bit mask to select a window with a depth buffer.

Description

The initial display mode is used when creating top-level windows, subwindows,and overlays to determine the OpenGL display mode for the to-be-created windowor overlay.


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glutInitWindowPosition, glutInitWindowSize

glutInitWindowPosition and glutInitWindowSize set the initial windowposition andsize respectively.

void glutInitWindowSize(int width, int height);

void glutInitWindowPosition(int x, int y);width

Width in pixels.height

Height in pixels.x

Window X location in pixels.y

Window Y location in pixels.

glutCreateWindow

glutCreateWindow creates a top-level window.

Usage

int glutCreateWindow(char *name);name

ASCII character string for use as window name.

DescriptionglutCreateWindow creates a top-level window. The name will beprovided to the window system as the window's name. The intent is that the

window system will label the window with the name.

Implicitly, the current window is set to the newly created window.


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glutDisplayFunc

glutDisplayFunc sets the display callback for the current window.

Usage

void glutDisplayFunc(void (*func)(void));func

The new display callback function.

Description

glutDisplayFunc sets the display callback for the current window. When GLUT

determines that the normal plane for the window needs to be redisplayed, thedisplay callback for the window is called. Before the callback, the current

window is set to the window needing to be redisplayed and (if no overlay displaycallback is registered) the layer in use is set to the normal plane. The displaycallback is called with no parameters. The entire normal plane region should be

redisplayed in response to the callback (this includes ancillary buffers if yourprogram depends on their state).


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glutMainLoop

glutMainLoop enters the GLUT event processing loop.

Usage

void glutMainLoop(void);

Description

glutMainLoop enters the GLUT event processing loop. This routine should becalled at most once in a GLUT program. Once called, this routine will never return.It will call as necessary any callbacks that have been registered.


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glutReshapeFunc

glutReshapeFunc sets the reshape callback for the current window.

Usage

void glutReshapeFunc(void (*func)(int width, int height));func

The new reshape callback function.

Description

glutReshapeFunc sets the reshape callback for the current window. The reshape

callback is triggered when a window is reshaped. A reshape callback is alsotriggered immediately before a window's first display callback after a window is

created or whenever an overlay for the window is established.The width and height parameters of the callback specify the new window size in

pixels. Before the callback, the current windowis set to the window that has beenreshaped.


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Name

glClearColor specify clear values for the color buffers

C Specificationvoid glClearColor( GLfloat red,

GLfloat green,

GLfloat blue,

GLfloat alpha);

Parameters

red, green, blue, alpha

Specify the red, green, blue, and alpha values used when the color buffers are cleared. Theinitial values are all 0.

Description

glClearColor specifies the red, green, blue, and alpha values used byglClearto clear the color

buffers. Values specified by glClearColor are clamped to the range 0 1 .
http://www.opengl.org/sdk/docs/man/xhtml/glClear.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glClear.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glClear.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glClear.xml


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Name

glClear clear buffers to preset values

C Specificationvoid glClear(GLbitfield mask);

Parameters

mask

Bitwise OR of masks that indicate the buffers to be cleared. The three masksare GL_COLOR_BUFFER_BIT, GL_DEPTH_BUFFER_BIT, and GL_STENCIL_BUFFER_BIT.

Description

glClear sets the bitplane area of the window to values previously selected

by glClearColor, glClearDepth, and glClearStencil. Multiple color buffers can be cleared

simultaneously by selecting more than one buffer at a time usingglDrawBuffer.

lClear takes a single argument that is the bitwise OR of several values indicating which buffer is to

be cleared.

The values are as follows:

GL_COLOR_BUFFER_BIT

Indicates the buffers currently enabled for color writing.

GL_DEPTH_BUFFER_BIT

Indicates the depth buffer.

GL_STENCIL_BUFFER_BIT

Indicates the stencil buffer.

The value to which each buffer is cleared depends on the setting of the clear value for that buffer.
http://www.opengl.org/sdk/docs/man/xhtml/glDrawBuffer.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glDrawBuffer.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glDrawBuffer.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glDrawBuffer.xml


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glColor3f() takes 3 arguments: the red, green and blue components of the color you want. After you

use glColor3f, everything you draw will be in that color. For example, consider this display function:


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Name

glBegin delimit the vertices of a primitive or a group of like primitives

C Specificationvoid glBegin(GLenum mode);

Parameters

mode

Specifies the primitive or primitives that will be created from vertices

presented between glBegin and the subsequentglEnd. Ten symbolic

constants areaccepted: GL_POINTS, GL_LINES, GL_LINE_STRIP,GL_LINE_LOOP, GL_TRIANGLES, G

L_TRIANGLE_STRIP, GL_TRIANGLE_FAN, GL_QUADS, GL_QUAD_STRIP,and GL_POLYGON.

C Specification

void glEnd(void);

DescriptionglBegin andglEnddelimit the vertices that define a primitive or a group of like

primitives. glBegin accepts a single argument that specifies in which of ten waysthe vertices are interpreted. Taking n as an integer count starting at one, and N asthe total number of vertices specified, the interpretations are as follows:

GL_POINTS

Treats each vertex as a single point. Vertex n defines point n. N points are

drawn.GL_LINES

Treats each pair of vertices as an independent line segment. Vertices 2 n -

1 and 2 n define line n. N 2 lines are drawn.

GL_LINE_STRIP

Draws a connected group of line segments from the first vertex to the last.Vertices n and n + 1 define line n. N - 1 lines are drawn.

GL_LINE_LOOP
http://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xml


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Draws a connected group of line segments from the first vertex to the last,

then back to the first. Vertices n and n + 1 define line n. The last line,

however, is defined by vertices N and 1 . N lines are drawn.

GL_TRIANGLES

Treats each triplet of vertices as an independent triangle. Vertices 3 n -

2 , 3 n - 1 , and 3 n define triangle n. N 3 triangles are drawn.

GL_TRIANGLE_STRIP

Draws a connected group of triangles. One triangle is defined for eachvertex presented after the first two vertices. For odd n, vertices n, n + 1 ,and n + 2 define triangle n. For even n, vertices n + 1 , n, and n + 2define

triangle n. N - 2 triangles are drawn.

GL_TRIANGLE_FAN

Draws a connected group of triangles. One triangle is defined for eachvertex presented after the first two vertices. Vertices 1 , n + 1 ,

and n + 2 define triangle n. N - 2 triangles are drawn.

GL_QUADS

Treats each group of four vertices as an independent quadrilateral.

Vertices 4 n - 3 , 4 n - 2 , 4 n - 1 , and 4 n definequadrilateral n. N 4 quadrilaterals are drawn.

GL_QUAD_STRIP

Draws a connected group of quadrilaterals. One quadrilateral is defined for

each pair of vertices presented after the first pair. Vertices 2 n -

1 , 2 n , 2 n + 2 , and 2 n + 1 define quadrilateral n. N 2 -

1quadrilaterals are drawn. Note that the order in which vertices are used toconstruct a quadrilateral from strip data is different from that used with

independent data.GL_POLYGON

Draws a single, convex polygon. Vertices 1 through N define this polygon.


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Name

glVertex specify a vertex

C Specificationvoid glVertex2s(GLshort ,

GLshort );void glVertex2i(GLint ,

GLint );void glVertex2f(GLfloat ,

GLfloat );void glVertex2d(GLdouble ,

GLdouble );void glVertex3s(GLshort ,

GLshort ,

GLshort );void glVertex3i(GLint ,

GLint ,

GLint );void glVertex3f(GLfloat ,

GLfloat ,

GLfloat );void glVertex3d(GLdouble ,

GLdouble ,

GLdouble );void glVertex4s(GLshort ,

GLshort ,

GLshort ,

GLshort w);void glVertex4i(GLint ,

GLint ,

GLint ,

GLint w);void glVertex4f(GLfloat ,

GLfloat ,

GLfloat ,GLfloat w);

void glVertex4d(GLdouble ,

GLdouble ,

GLdouble ,

GLdouble w);

Parameters

x, y, z, w


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Specifyx,y,z, and w coordinates of a vertex. Not all parameters are present

in all forms of the command.

C Specification

void glVertex2sv(const GLshort * v);void glVertex2iv(const GLint * v);void glVertex2fv(const GLfloat * v);void glVertex2dv(const GLdouble * v);void glVertex3sv(const GLshort * v);void glVertex3iv(const GLint * v);void glVertex3fv(const GLfloat * v);void glVertex3dv(const GLdouble * v);void glVertex4sv(const GLshort * v);void glVertex4iv(const GLint * v);void glVertex4fv(const GLfloat * v);void glVertex4dv(const GLdouble * v);

Parameters

v

Specifies a pointer to an array of two, three, or four elements. The elementsof a two-element array are x and y; of a three-element array, x, y, and z; and

of a four-element array, x, y, z, and w.

Description

glVertex commands are used withinglBegin/glEndpairs to specify point, line, andpolygon vertices. The current color, normal, texture coordinates, and fogcoordinate are associated with the vertex when glVertex is called.

When only x and y are specified, z defaults to 0 and w defaults to 1. When x, y,and z are specified, w defaults to 1.
http://www.opengl.org/sdk/docs/man2/xhtml/glBegin.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glBegin.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glEnd.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glBegin.xml


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glutSwapBuffers

glutSwapBuffers swaps the buffers of the current window if double buffered.

Usage

void glutSwapBuffers(void);

Description

Performs a buffer swap on the layer in use for the current window.

Specifically, glutSwapBuffers promotes the contents of the back buffer of the layerin use of the current window to become the contents of the front buffer. The

contents of the back buffer then become undefined. The update typically takes

place during the vertical retrace of the monitor, rather than immediatelyafterglutSwapBuffers is called.

An implicit glFlush is done by glutSwapBuffers before it returns.

glFlush force execution of GL commands in finite time

C Specification

void glFlush(void);

Description

Different GL implementations buffer commands in several different locations, including networkbuffers and the graphics accelerator itself. glFlush empties all of these buffers, causing all issued

commands to be executed as quickly as they are accepted by the actual rendering engine. Thoughthis execution may not be completed in any particular time period, it does complete in finite time.

Because any GL program might be executed over a network, or on an accelerator that buffers

commands, all programs should call glFlush whenever they count on having all of their previouslyissued commands completed. For example, call glFlush before waiting for user input that depends

on the generated image.


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glViewport set the viewport

C Specification

void glViewport( GLint x,

GLint y,

GLsizei width,

GLsizei height);

Parameters

x, y

Specify the lower left corner of the viewport rectangle, in pixels. The initial value is (0,0).

width, height

Specify the width and height of the viewport. When a GL context is first attached to a

window, width and heightare set to the dimensions of that window.

Description

glViewport specifies the affine transformation of x and y from normalized device coordinates to

window coordinates. Let x nd y nd be normalized device coordinates. Then the window

coordinates x w y w are computed as follows:

x w = x nd + 1 width 2 + x

y w = y nd + 1 height 2 + y

Viewport width and height are silently clamped to a range that depends on the implementation. To

query this range, callglGetwith argument GL_MAX_VIEWPORT_DIMS.
http://www.opengl.org/sdk/docs/man/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man/xhtml/glGet.xml


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glMatrixMode specify which matrix is the current matrix

C Specification

void glMatrixMode(GLenum mode)

;

Parameters

mode

Specifies which matrix stack is the target for subsequent matrix operations.

Three values are accepted: GL_MODELVIEW, GL_PROJECTION, and GL_TEXTURE.

The initial value is GL_MODELVIEW. Additionally, if theARB_imaging extension

is supported, GL_COLOR is also accepted.

Description

glMatrixMode sets the current matrix mode. mode can assume one of four values:

GL_MODELVIEW

Applies subsequent matrix operations to the modelview matrix stack.

GL_PROJECTION

Applies subsequent matrix operations to the projection matrix stack.

GL_TEXTURE

Applies subsequent matrix operations to the texture matrix stack.

GL_COLOR

Applies subsequent matrix operations to the color matrix stack.

To find out which matrix stack is currently the target of all matrix operations,callglGetwith argument GL_MATRIX_MODE. The initial value is GL_MODELVIEW.
http://www.opengl.org/sdk/docs/man2/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glGet.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glGet.xml


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NAMEglLoadIdentity - replace the current matrix with theidentity matrix

CSPECIFICATION

void glLoadIdentity( void )

DESCRIPTIONglLoadIdentity replaces the current matrix with the identitymatrix. It is semantically equivalent to callingglLoadMatrix with the identity matrix

( 1 0 0 0 )| || 0 1 0 0 || 0 0 1 0 |

| |( 0 0 0 1 )

but in some cases it is more efficient.


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gluLookAt define a viewing transformation

C Specification

void gluLookAt(GLdouble eyeX,

GLdouble eyeY,

GLdouble eyeZ,

GLdouble centerX,

GLdouble centerY,

GLdouble centerZ,

GLdouble upX,

GLdouble upY,

GLdouble upZ);

Parameters

eyeX, eyeY, eyeZ

Specifies the position of the eye point.

centerX, centerY, centerZ

Specifies the position of the reference point.

upX, upY, upZ

Specifies the direction of the up vector.

Description

gluLookAt creates a viewing matrix derived from an eye point, a reference point

indicating the center of the scene, and an UPvector.

The matrix maps the reference point to the negativezaxis and the eye point to theorigin. When a typical projection matrix is used, the center of the scene thereforemaps to the center of the viewport. Similarly, the direction described by

the UPvector projected onto the viewing plane is mapped to the positivey axis so


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that it points upward in the viewport. The UPvector must not be parallel to the line

of sight from the eye point to the reference point.

Let

F = centerX - eyeX centerY - eyeY centerZ - eyeZ

Let UPbe the vector upX upY upZ .

Then normalize as follows:

f = F F

UP = UP UP

Finally, let s = f UP , and u = s f .

M is then constructed as follows:

M = s 0 s 1 s 2 0 u 0 u 1 u 2 0 - f 0 - f 1 - f 2 0 0 0 0 1

and gluLookAt is equivalent to

glMultMatrixf(M);glTranslated(-eyex, -eyey, -eyez);


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gluPerspective set up a perspective projection matrix

C Specification

void gluPerspective(GLdouble ovy,

GLdouble aspect,

GLdouble zNear,

GLdouble zFar);

Parameters

fovy

Specifies the field of view angle, in degrees, in they direction.

aspect

Specifies the aspect ratio that determines the field of view in the x direction.The aspect ratio is the ratio ofx (width) toy (height).

zNear

Specifies the distance from the viewer to the near clipping plane (alwayspositive).

zFar

Specifies the distance from the viewer to the far clipping plane (always

positive).

Description

gluPerspective specifies a viewing frustum into the world coordinate system. In

general, the aspect ratio in gluPerspective should match the aspect ratio of the

associated viewport. For example, aspect = 2.0 means the viewer's angle of view istwice as wide inx as it is iny. If the viewport is twice as wide as it is tall, it

displays the image without distortion.

The matrix generated by gluPerspective is multipled by the current matrix, just asifglMultMatrixwere called with the generated matrix. To load the perspectivematrix onto the current matrix stack instead, precede the call

to gluPerspective with a call toglLoadIdentity.
http://www.opengl.org/sdk/docs/man2/xhtml/glMultMatrix.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glMultMatrix.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glMultMatrix.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glLoadIdentity.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glLoadIdentity.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glLoadIdentity.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glLoadIdentity.xmlhttp://www.opengl.org/sdk/docs/man2/xhtml/glMultMatrix.xml


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Givenfdefined as follows:

f = cotangent fovy 2

The generated matrix is

f aspect 0 0 0 0 f 0 0 0 0 zFar + zNear zNear - zFar 2 zFar zNear zNear -

zFar 0 0 -1 0


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gluOrtho2D define a 2D orthographic projection matrix

C Specification

void gluOrtho2D(GLdouble left,

GLdouble right,

GLdouble bottom,

GLdouble top);

Parameters

left, right

Specify the coordinates for the left and right vertical clipping planes.

bottom, top

Specify the coordinates for the bottom and top horizontal clipping planes.

Description

gluOrtho2D sets up a two-dimensional orthographic viewing region.


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