3.B] Explain different OpenGL routines used for manipulating the display window.

Answer:-

OpenGL Routines for Manipulating the Display Window

1. glViewport

Purpose: Defines the portion of the window where the rendering will take place.

Usage: Sets up the viewport dimensions, which specify how OpenGL coordinates map to window coordinates.

void glViewport(GLint x, GLint y, GLsizei width, GLsizei height);

Example:

glViewport(0, 0, 800, 600);  // Set viewport to cover the entire window

2. glScissor

Purpose: Defines a rectangular region of the window where rendering can occur.

Usage: Restricts drawing to a specific area using the scissor box.

void glScissor(GLint x, GLint y, GLsizei width, GLsizei height);

Example:

glEnable(GL_SCISSOR_TEST);  // Enable scissor test
glScissor(100, 100, 400, 300);  // Set scissor box

3. glClear

Purpose: Clears the buffers to preset values.

Usage: Typically called at the beginning of the rendering process to prepare the window for drawing.

void glClear(GLbitfield mask);

Example:

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);  // Clear color and depth buffers

4. glClearColor

Purpose: Sets the color used when clearing the color buffer.

Usage: Defines the clear color used by glClear.

void glClearColor(GLfloat red, GLfloat green, GLfloat blue, GLfloat alpha);

Example:

glClearColor(0.0f, 0.0f, 0.0f, 1.0f);  // Set clear color to black

5. glFlush

Purpose: Forces the execution of all previously issued OpenGL commands.

Usage: Ensures that rendering commands are processed immediately.

void glFlush(void);

6. glFinish

Purpose: Blocks until all OpenGL commands are finished executing.

Usage: Ensures that all rendering commands are complete before continuing.

void glFinish(void);

7. glDrawBuffer

Purpose: Selects the color buffer to which subsequent drawing commands will be directed.

Usage: Allows you to specify which color buffer (e.g., front, back) to draw to.

void glDrawBuffer(GLenum mode);

Example:

glDrawBuffer(GL_BACK);  // Draw to the back buffer

8. glReadBuffer

Purpose: Specifies which color buffer to read from.

Usage: Determines the color buffer from which pixels will be read (e.g., front, back).

void glReadBuffer(GLenum mode);

Example:

glReadBuffer(GL_FRONT);  // Read from the front buffer