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# Important Short Questions and Answers: Computer Graphics - Illumination and Colour Models

Computer Graphics and Architecture -

The shading model attempts to model how light that emanates from light sources would interact with objects in a scene. The shading model dictates how light is scattered or reflected from a surface

2.What is known as black body?

If all of the incident light is absorbed, the object appears black and is known as a blackbody.

3.State Lamber’s Law?

The relationship between brightness and surface orientation is called lamber’s law.

4.What are the three types of light contributions? Diffuse

Specular

Ambient

5.What are the two types of smooth shading? The 2 types of smooth shading are

Greater realism can be achieved, to highlights on shiny objects, by a better approximation of the normal vector to the face at each pixel. This type of shading is called phong shading.

7.What is called texels?

Textures are formed bitmap representations of images. Such representation consists of an array, such as texture [c] [r], of color values called texels.

8.What is the use of glGetUniformLocation function?

The glGetUniformLocation function is used to retrieve the locations of some uniform variables that are defined in the shaders.

10.Write down the function of texture(s,t)?

The function texture (s,t) accesses “samples” in the array, as in the code,

Color3 texture(float s, float t)

{

Return txtr[(int)(s*c)][(int)(t*R)];

}

11.What is the visible intensity?

The visible intensity I is set equal to the texture value at each spot.

I= texture(s,t)

12.What is the use of glTexCoord2f() function?

The function glTexCoord2f() is used to associate a point in texture space, Pi=(si,ti) with each vertex Vi of the face.

13.Write down the OpenGL command to define a quadrilateral face. glBegin(GL_QUADS);//define a quadrilateral face glTexCoord2f(0.0,0.0); glVertex3f(1.0,2.5,1.5); glTexCoord2f(0.0,0.6);glVertex3f(1.0,3.7,1.5); glTexCoord2f(0.8,0.6);glVertex(2.0,3.7,1.5); glTexCoord2f(0.8,0.0);glVertex3f(2.0,2.5,1.5); glEnd();

14.Give the basic idea of reflection Mapping.

The reflection mapping can significantly improve the realism of pictures especially animations. The basic idea is to see reflections in an object thet suggest the “world”

surrounding thet object.

5.What is called a shadow buffer?

An auxiliary second depth buffer,called a shadow buffer,is employed for each light source. It contains depth picture for the scene from the point of view of the light source.

16.What does sliding means?

Sliding means to move the camera along one of its own axes,(ie) in the u,v or n directions,without rotating it.

17.Write down the syntax for glFramebufferRenderbufferEXT(). Void glFramebufferRenderbufferEXT(GLenum target,

GLenum attachmentPoint,

GLenum renderbufferTarget,

GLuint renderbufferId);

18.What is the function of glCheckFramebufferStatusEXT()?

The glCheckFramebufferStatusEXT() validates all its attached images and framebuffer parameters on the currently bound FBO. And, this function cannot be called within glBegin()/glEnd() pair.

19.Write down the syntax for glGetRenderbufferParameteriveEXT().

Void glGetRenderbufferParameterivEXT(GLenum target, GLenum param, Glint* value);

20.List out some of the rules of FBO completeness.

The width and height of framebuffer-attachable image must be not zero

FBO must have at least one image attached

All images attached a FBO must have the same width and height

All images attached the color attachment points must have the same internal format.

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