Diffuse and Specular lighting

AJ2112

Hi, I understand what diffuse and specular light are by 3D definition, but a bit confused.  Is pointlight, spotlight, distant light, etc.... diffuse and specular lights ?  or is diffuse and specular light a specific stand alone light prop ?  Or can any light be used, differences would be in surface parameters, diffuse and specular ? 

Architectural lighting rig at store has 8 Normal Spotlights and 8 Specular Spotlights.  How is either spotlights made different ?  

Thanks for any assistance.   

ebergerly

Actually diffuse and specular define how a surface reflects light. Shiny "specular" surfaces like chrome are very flat and smooth, and therefore have sharp reflections like a mirror. Bumpy "diffuse" surfaces like a fabric reflect light but the light gets "diffused" and doesn't give a shiny reflection. 

For light sources you can have light rays coming out in a very uniform pattern (like at right angles to the bulb or whatever surface is emitting light), or you can have a light source emitting light at random angles. Real light sources like light bulbs with a "frosted" glass have light rays coming out at random angles as they bounce thru the frosted surface. But the included light sources in Studio are generally uniform emitters which don't really act like real world lights. 

What I do is add an object to the scene that looks like the light bulb I'm trying to simulate and add an emissive surface to it. That tends to simulate light rays more realistically, coming out at random angles.  

AJ2112

Thanks friend.

Szark

Well to be more correct a diffuse light in a 3DL sense will only light the diffuse and not the specular and vice versa so you can control how much light the surface gets for each. However I tested this in Iray and from what I can tell it isn't working like 3DL, in fact I get the same result with either so I am not why Iray lights have this setting at all. I only tested spots

Linwelly

Szark said:

Well to be more correct a diffuse light in a 3DL sense will only light the diffuse and not the specular and vice versa so you can control how much light the surface gets for each. However I tested this in Iray and from what I can tell it isn't working like 3DL, in fact I get the same result with either so I am not why Iray lights have this setting at all. I only tested spots

As Iray is supposed to be a physical renderer there are no two different light types possible like in 3dl, so this option only works for 3delight

Szark

exactly what I thought Linwelly

DustRider

However, you can fake diffuse only lights in Iray by using mesh lights that have the cutout opacity set to a near zero value (what people often call ghost lights, after the product with that name in the store). Since the light is virtually invisible, it will add a virtually no specular reflection to items in the image, but will increase the amount of light in the image.

AlmightyQUEST

The product in question with diffuse and specular lights is for 3Delight, yes. There is a separate iray version of the product.

AJ2112

Thanks friends, PBR guide states: The major building blocks of the Phong model consist of 3 components: ambient, diffuse and specular lighting. Below you can see what these lighting components actually look like:

 

 

Szark

 but in Iray you can't split them off like you can in 3DL. There is no ambient in Iray only light, Specular, Diffuse and Emission (light emitting). Well there is ambient obviously but it is automatic hard coded in the render engine.  

AJ2112

Gotcha, thanks Pete