Lighting

I don't really understand where you get your normal from. The normal is a vector that's perpendicular to the plane you are lighting. It doesn't belong to the light, it belongs to the surface. And why is the finalColour in the light struct? Every point you light will get it's own finalColour.

You seem to want to do diffuse and ambient lighting. This is pretty easy:

For every point you want to light, you need the normal. If you don't want smooth shading, this is just the normal of the polygon that point lays on.
Now you need two vecters. First the light vector. This vector points in the direction of the light, and has length one:

VECTOR3D lightVec = light.pos - point.pos;
lightVec.Normalize();

the normal is usually precalculated

Now we take the (3D) dot product of these two vectors to calculate the light intensity:
float theta = DotProduct(lightVec,point.normal);

finalColour = diffuse * theta + ambient;

This takes only the incidence angle into account. If you want it to look good, you need some sort of attenuation. By example linear attenuation:

float lightDist = sqrtf(lightVec.x * lightVec.x + lightVec.y * lightVec.y + lightVec.z * lightVec.z);
float falloff = 1 - lightDist / range;
if(falloff < 0)
falloff = 0;

finalColour = (diffuse * theta + ambient) * falloff;

This is for point lights btw. for directional lights it's even easier. The lightVec is a fixed vector, and there's no attenuation.

My Site

[edited by - Quasar3D on December 29, 2003 8:31:08 AM]

quote:

---

Original post by quasar3d
I don''t really understand where you get your normal from. The normal is a vector that''s perpendicular to the plane you are lighting. It doesn''t belong to the light, it belongs to the surface. And why is the finalColour in the light struct? Every point you light will get it''s own finalColour.

You seem to want to do diffuse and ambient lighting. This is pretty easy:

---

Thats correct, I want to only do diffuse and ambient lighting at the moment before going further. The finalColor contains x,y,z,w which would analogous to r, g, b, a.

quote:

---

Original post by quasar3d
For every point you want to light, you need the normal. If you don''t want smooth shading, this is just the normal of the polygon that point lays on.

---

I am doing it in using smooth shading so I would assume I need a normal for every vertex.

quote:

---

Original post by quasar3d
Now you need two vecters. First the light vector. This vector points in the direction of the light, and has length one:

VECTOR3D lightVec = light.pos - point.pos;
lightVec.Normalize();

the normal is usually precalculated

Now we take the (3D) dot product of these two vectors to calculate the light intensity:
float theta = DotProduct(lightVec,point.normal);

finalColour = diffuse * theta + ambient;

This takes only the incidence angle into account. If you want it to look good, you need some sort of attenuation. By example linear attenuation:

float lightDist = sqrtf(lightVec.x * lightVec.x + lightVec.y * lightVec.y + lightVec.z * lightVec.z);
float falloff = 1 - lightDist / range;
if(falloff < 0)
falloff = 0;

finalColour = (diffuse * theta + ambient) * falloff;

This is for point lights btw. for directional lights it''s even easier. The lightVec is a fixed vector, and there''s no attenuation.

---

I did it like this without the falloff and partly it seems to work. But it seems to do constant coloring everywhere. This I do not wish to happen. The coloring seems to be constant. Should I be using face normals or vertex normals. At the point I am calculating normals per vertex (I guess you call these psuedo normals or something).

quote:

---

Original post by CRACK123
light.position.set(0, 0, 1, 0);
vector4 pos(position);
vector4 dir = light.position - pos;
vector3 n = Normalized(position);
vector4 normal(n);

float theta = DotProduct(normal, dir.normalize());
[/source]

---

Why do you set the normal to the normalized position here? The normal is included in the vertex, right?

quote:

---

Original post by quasar3d

quote:

---

Original post by CRACK123
light.position.set(0, 0, 1, 0);
vector4 pos(position);
vector4 dir = light.position - pos;
vector3 n = Normalized(position);
vector4 normal(n);

float theta = DotProduct(normal, dir.normalize());
[/source]

---

Why do you set the normal to the normalized position here? The normal is included in the vertex, right?

---

Hey, I made a mistake there. Yes, the normal is already already there. I am using the normal of the 3D model file itself. But using the normals too it colors everything, it doesn't show any kind of lighting effect. It seems to apply same color to all vertices. So its like constant everywhere.

[edited by - CRACK123 on December 30, 2003 6:07:00 PM]