Chapter 8: Putting it Together | The Ray Tracer Challenge

mk
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Posts: 4

Chapter 8: Putting it Together Jun 19, 2022 0:52:05 GMT

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Post by mk on Jun 19, 2022 0:52:05 GMT

Hello, I have really been enjoying the book so far. I've run across a bit of a hurdle on the final part of chapter 8 using the same scene from the end of chapter 7. I've re-passed every test from chapters 1-8. The proper lighting that was present in my image at the end of chapter 7 is no longer appearing.
My code is here: github.com/matt-kerr/KerrEngine
The test is setup in KerrTester.cpp and debug can be toggled in KerrEngine.h.

Spheres

For any given point my t values computed from World::isShadowed always end up negative or 0, causing the function to always return true. Here is some output from a random point (from the lower 80x60 image). Thank you in advance!

(x=40, y=18)

Camera::rayForPixel values:

    xoffset = 0.584567

    yoffset = 0.267024

    world_x = -0.00721688

    world_y = 0.165988

    pixel = point(0.00725287, 1.56648, -3.98836, 1)

    returning Ray:

    origin = point(0, 1.5, -5, 1)

    direction = vector(0.00715402, 0.0655783, 0.997847, 0)



World::colorAt entered function, calculating world/ray intersection

    World::intersectWorld entered

    World::intersectWorld testing sphere 1

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -1159.74, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 0

    World::intersectWorld testing sphere 2

        Ray::intersectSphere entered

        Ray::intersectSphere a = 4907.37

        Ray::intersectSphere b = -99069.4

        Ray::intersectSphere c = 500000

        Ray::intersectSphere discriminant = 18710

        Ray::intersectSphere t1 = 10.08

        Ray::intersectSphere t2 = 10.1079

        Ray::intersectSphere exiting

    World::intersectWorld curr.size() = 2

    World::intersectWorld xs.size() = 2

    World::intersectWorld testing sphere 3

        Ray::intersectSphere entered

        Ray::intersectSphere a = 5050.14

        Ray::intersectSphere b = -100500

        Ray::intersectSphere c = 500000

        Ray::intersectSphere discriminant = 19262.6

        Ray::intersectSphere t1 = 9.93649

        Ray::intersectSphere t2 = 9.96398

        Ray::intersectSphere exiting

    World::intersectWorld curr.size() = 2

    World::intersectWorld xs.size() = 4

    World::intersectWorld testing sphere 4

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -0.117829, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 4

    World::intersectWorld testing sphere 5

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -228.981, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 4

    World::intersectWorld testing sphere 6

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -1458.08, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 4

    World::intersectWorld after sort:

            xs[0].t = 9.93649

            xs[1].t = 9.96398

            xs[2].t = 10.08

            xs[3].t = 10.1079

    World::intersectWorld exiting

World::colorAt xs.size() = 4

World::colorAt xs[0].t = 9.93649

World::colorAt xs[1].t = 9.96398

World::colorAt xs[2].t = 10.08

World::colorAt xs[3].t = 10.1079

Computations::prepareComputations returning

    t = 9.93649

    obj.material.color  = color(1.000000, 1.000000, 1.000000)

    point = point(0.0710858, 2.15162, 4.9151, 1)

    eyev = vector(-0.00715402, -0.0655783, -0.997847, 0)

    normalv = vector(-0.999977, 0.000311599, -1, 0)

    inside = 0

World::colorAt i.t = 9.93649

World::colorAt comps.t = 9.93649

World::colorAt calculating shadeHit = 9.93649

World::shadeHit comps.t = 9.93649

World::isShadowed entered

    World::intersectWorld entered

    World::intersectWorld testing sphere 1

        Ray::intersectSphere entered

        Ray::intersectSphere a = 2168.48

        Ray::intersectSphere b = 20038.7

        Ray::intersectSphere c = 46293.9

        Ray::intersectSphere discriminant = 946.064

        Ray::intersectSphere t1 = -4.62754

        Ray::intersectSphere t2 = -4.61336

        Ray::intersectSphere exiting

    World::intersectWorld curr.size() = 2

    World::intersectWorld xs.size() = 2

    World::intersectWorld testing sphere 2

        Ray::intersectSphere entered

        Ray::intersectSphere a = 413.037

        Ray::intersectSphere b = 448.328

        Ray::intersectSphere c = 120.698

        Ray::intersectSphere discriminant = 1587.41

        Ray::intersectSphere t1 = -0.590952

        Ray::intersectSphere t2 = -0.49449

        Ray::intersectSphere exiting

    World::intersectWorld curr.size() = 2

    World::intersectWorld xs.size() = 4

    World::intersectWorld testing sphere 3

        Ray::intersectSphere entered

        Ray::intersectSphere a = 10989.1

        Ray::intersectSphere b = 204.755

        Ray::intersectSphere c = 0

        Ray::intersectSphere discriminant = 41924.7

        Ray::intersectSphere t1 = -0.0186325

        Ray::intersectSphere t2 = 0

        Ray::intersectSphere exiting

    World::intersectWorld curr.size() = 2

    World::intersectWorld xs.size() = 6

    World::intersectWorld testing sphere 4

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -54.2343, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 6

    World::intersectWorld testing sphere 5

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -2296.53, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 6

    World::intersectWorld testing sphere 6

        Ray::intersectSphere entered

        Ray::intersectSphere discriminant = -8502.38, returning early

    World::intersectWorld curr.size() = 0

    World::intersectWorld xs.size() = 6

    World::intersectWorld after sort:

            xs[0].t = -4.62754

            xs[1].t = -4.61336

            xs[2].t = -0.590952

            xs[3].t = -0.49449

            xs[4].t = -0.0186325

            xs[5].t = 0

    World::intersectWorld exiting

World::isShadowed world.light.position = point(-10, 10, -10, 1)

World::isShadowed point = point(0.0710858, 2.15162, 4.9151, 1)

World::isShadowed v = vector(-10.0711, 7.84838, -14.9151, 0)

World::isShadowed distance = 16.854

World::isShadowed direction = vector(-0.597549, 0.465669, -0.884959, 0)

World::isShadowed xs.size() = 6

World::isShadowed xs[0].t = -4.62754

World::isShadowed xs[1].t = -4.61336

World::isShadowed xs[2].t = -0.590952

World::isShadowed xs[3].t = -0.49449

World::isShadowed xs[4].t = -0.0186325

World::isShadowed xs[5].t = 0

World::isShadowed ht_adj = 0

World::isShadowed returning true

World::shadeHit comps.t = 9.93649

World::shadeHit comps.point = point(0.0710858, 2.15162, 4.9151, 1)

World::shadeHit comps.over_point = point(0.0710858, 2.15162, 4.9151, 1)

World::shadeHit shadowed = 1

World::shadeHit returning color(0.100000, 0.100000, 0.100000)

Last Edit: Jul 3, 2022 0:34:10 GMT by mk

Jamis
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Posts: 310

Chapter 8: Putting it Together Jun 22, 2022 2:38:37 GMT

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Post by Jamis on Jun 22, 2022 2:38:37 GMT

Hey mk -- I *think* the issue is in your isShadowed method. You're not ignoring intersections that are behind the point of origin. At github.com/matt-kerr/KerrEngine/blob/master/World.cpp#L123, you're setting (e.g.) -EPSILON to 0, and at github.com/matt-kerr/KerrEngine/blob/master/World.cpp#L123, you're allowing anything less than the distance to the light source (including 0) to cast a shadow. I think what you want is to change line 123 to something like:

if (ht_adj > 0 && ht_adj < distance)

Does that make any difference?

mk
New Member

Posts: 4

Chapter 8: Putting it Together Jun 22, 2022 17:27:47 GMT

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Post by mk on Jun 22, 2022 17:27:47 GMT

Thanks for the assistance. I changed the line to be ht_adj > 0.0 && ht_adj < distance. The scene is starting to look better. I made a small testing change so that anything returned true by isShadowed is colored red. It seems the "floor" shadow is not appearing at all and the material effects are producing too much white on the spheres.

Last Edit: Jul 3, 2022 0:34:41 GMT by mk

mk
New Member

Posts: 4

Chapter 8: Putting it Together Jun 27, 2022 3:15:42 GMT

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Post by mk on Jun 27, 2022 3:15:42 GMT

Hello,

I found that my hit function was returning the first t value >= 0 when it needed to be > 0. This fixed the shadow issue but the specular is still acting up. I'll update again once I find what is causing this!

In the Material::lighting function at (28,27) on an 80x60 canvas the reflect_dot_eye dot product uses reflectv = vector(0.742772, 0.108098, -0.990684) and evev = vector(0.108448, 0.0200543, -0.999799) calculating to 1.07321. The material has a default shininess of 200. The factor is then calculated to be a very large number from pow(1.07321, 200). This causes the specular to be color(410838.445378, 410838.445378, 410838.445378).

One pixel to the right at (33,24) I get reflectv = vector(0.867024, 0.0699223, -0.900552) and evev = vector(0.0939887, 0.0200543, -0.999799) calculating reflect_dot_eye to 0.983264. The resulting color is within an expected range color(0.083363, 0.375776, 0.741293).

Last Edit: Jun 27, 2022 4:29:01 GMT by mk

mk
New Member

Posts: 4

Chapter 8: Putting it Together Jun 28, 2022 0:17:59 GMT

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Post by mk on Jun 28, 2022 0:17:59 GMT

Finally figured it out! My Matrix::magnitude function was returning sqrt( + pow(m(1, 0), 2) + pow(m(2, 0), 2)); I forgot the x component and the compiler did not have any issue or warning about the expression starting with a + sign.

Last Edit: Jul 3, 2022 0:34:59 GMT by mk