Ch 11 Reflection / Refraction Problem

Hello totally! It looks like your renderer is on the right track, but yeah, something's not quite right. Do you have your source code anywhere I could take a look at it?

- Jamis

Thank you so much for the help chrisd & Jamis I will try to see how my numbers compare to those.

I did also notice trying to play with a simpler scene that things appear to start going wrong when I enable Schlick in the refraction / reflection calculation.

I believe that is where I should investigate further. I can post a better image later of what is happening.

Thanks again for the help!

That is really strange! Looking through your code, I'm not seeing anything obviously incorrect. What values for t do you get at that first intersection? And what is the index of refraction for the shape at each intersection? Here's what I get, iterating over xs just before computing n1 and n2 at the pixel at 125,125:

t(4.028495994977554) ior(1.5)
t(4.568385678150166) ior(1.0000034)
t(5.4176686785389325) ior(1.0000034)
t(5.957558361711545) ior(1.5)
t(15.020949740457555) ior(1)

A little more detail in this specific area Jamis 

My first time into prepareComputations things look like this:

The value of intersection which is my hit is the large sphere with:
t = 4.028495994977554

xs is as i posted above:

t(4.028495994977554) ior(1.5) ID:BIG-SPHERE
t(4.568385678150166) ior(1.0000034) ID:SMALL-SPHERE
t(5.4176686785389325) ior(1.0000034) ID:SMALL-SPHERE
t(5.957558361711545) ior(1.5) ID:BIG-SPHERE
t(15.020949740457555) ior(1) ID:WALL

So on the loop through the xs intersections, the first time through hit matches the first item.

This is the loop i have there that gives the n1 and n2 values from this data:

This is where I can not see how I would get something other can 1.0 for n1

Any thoughts would be greatly appreciated! 


for (let n = 0; n < xs.length; n++) {
     const i = xs[n];
     if (i === intersection) {
       if (containers.length === 0) {
         comps.n1 = 1.0;
       } else {
         comps.n1 = containers[containers.length - 1].material.refractiveIndex;
       }
     }
     const objectIndex = containers.indexOf(i.object);
     if (objectIndex !== -1) {
       containers.splice(objectIndex, 1);
     } else {
       containers.push(i.object);
     }
     if (i === intersection) {
       if (containers.length === 0) {
         comps.n2 = 1.0;
       } else {
         comps.n2 = containers[containers.length - 1].material.refractiveIndex;
       }
       break;
     }
   }


I think tdaines might have nailed it. Good catch! Definitely preserve all intersections, even those behind the eye (t < 0). They're used here to determine which shapes you're inside of, so that the initial refractive index is initialized correctly. (They'll be used later, too, when you get to the chapter on CSG.)

can you let me know if you found what was the problem because I tried to render the scene that jamis gave to you but i ended up with the scene image with yours:

Floor = Plane()

Floor.material = Material()

Floor.transform = NumpyMatrixMultiply(rotation_x(pi/2), translationMatrix(0, 0, 10))

Floor.material.pattern = CheckerPattern(Color(0.15, 0.15, 0.15), Color(0.85,0.85, 0.85))

Floor.material.ambient = 0.8

Floor.material.diffuse = 0.2

Floor.material.specular = 0;



glassSphere = Sphere()

glassSphere.material = Material()

glassSphere.material.diffuse = 0.1

glassSphere.material.shininess = 300.0

glassSphere.material.transparency = 0.9

glassSphere.material.reflective = 0.9

glassSphere.material.refractive_index = 1.52

glassSphere.material.ambient = 0

glassSphere.material.color = Color.White()

glassSphere.material.specular = 0.9

# glassSphere.transform = scaling(0.5, 0.5, 0.5)



airSphere = Sphere()

airSphere.transform = scaling(0.5, 0.5, 0.5)

airSphere.material = Material()

airSphere.material.color = Color.White()

airSphere.material.diffuse = 0

airSphere.material.shininess = 300.0

airSphere.material.reflective = 0.9

airSphere.material.transparency = 0.9

airSphere.material.ambient = 0

airSphere.material.specular = 0.9

airSphere.material.refractive_index = 1.0000034





world = World()

world.Objects = [Floor, airSphere, glassSphere]

world.light = PointLight(Point(2, 10, -5), Color(0.9, 0.9, 0.9))



cam = Camera(800, 800, 0.45)



cam.transform = view_transform(Point(0,0, -5), Point(0, 0, 0), Vector3(0, 1, 0))