DirectX - Lighting

DirectX is known for creating lights which is similar to real world lighting. It includes a system of varied calculation which is less time consuming and demonstrates the real world system. Lighting is considered as an important part of 3D game programming. Lighting helps user to bring the realism out and make it as a real time experience. The DirectX system includes built up of various set of types like lightning and types of light sources. Now, it is important to focus on three types of lightning as mentioned below −

Diffuse Lighting
Ambient Lighting
Specular Lighting

Diffuse Lighting

Diffuse light is a dim light which falls on the surface. The best demonstration is a user holding up hand with this light source. It will be visible that one side of hand is lit while the other side is not. The side which is lit is called as diffuse light and the procedure is called diffuse lighting.

Ambient Lighting

Ambient light refers to the light which spreads everywhere. As per the previous example, holding up the arm with one light source, the dark side is called as lightly lit or ambient lit. The light which is reflected is considered as ambient light and the process is called as ambient lighting.

Specular Light

Specular light is also called as specular highlight or even more commonly as reflection. When light reflects off the required object, usually most of the light will go in one specific direction.

Creating Lights

This section includes the process of creating lights which is often used for creating lights. Following are the important steps needed for creating lights −

Starting with new flexible format
Process of turning light on
Ambient light setup
Diffuse light setup
Setting the material standards

The first three are considered as simple processes, but the last two will require a whole function to themselves.

Starting with new flexible format

Once again, we will focus on the FVF code and the vertex format will change. This time we are focusing on the diffuse color and add a new property in the vertex normal. The new FVF code and vertex format is mentioned below −

struct CUSTOMVERTEX {FLOAT X, Y, Z; D3DVECTOR NORMAL;};
#define CUSTOMFVF (D3DFVF_XYZ | D3DFVF_NORMAL)
D3DVECTOR NORMAL;
#definition of the structure
typedef struct D3DVECTOR {
   float x, y, z;
} D3DVECTOR, *LPD3DVECTOR;

Process of turning light on

The function call is already discussed in the previous sections. The process of activating the lights on is given in the following code −

d3ddev->SetRenderState(D3DRS_LIGHTING, TRUE);

Ambient Light setup

This step uses the same particular function, SetRenderState which is considered as the first parameter that changes to a different flag, the second parameter is D3DRS_AMBIENT which is color of the ambient light.

d3ddev->SetRenderState(D3DRS_AMBIENT, D3DCOLOR_XRGB(50, 50, 50)); // ambient light

Diffusion of light setup

This step is longer than normal. It is important for the properties of the size and flexibility of this step, with its own function called own_light(). It is given below −

this is the function that sets up the lights and materials
void init_light(void){
   D3DLIGHT9 light; // creating the structure of light
   ZeroMemory(&light, sizeof(light)); // following zero memory pattern
   light.Type = D3DLIGHT_DIRECTIONAL; // creating the light type
   light.Diffuse = D3DXCOLOR(0.5f, 0.5f, 0.5f, 1.0f); // setting up the color
   light.Direction = D3DXVECTOR3(-1.0f, -0.3f, -1.0f);
   d3ddev->SetLight(0, &light); // send the light struct properties to light #0
   d3ddev->LightEnable(0, TRUE); // turn on light #0
}

D3DLIGHT9

D3DLIGHT9 is a struct data which includes all the information about a light, no matter what its type is.

The demonstration of the lit cube is mentioned below −