Chapter 11 - Transparent Objects are not rendered correctly

blork98
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Posts: 5

Chapter 11 - Transparent Objects are not rendered correctly Feb 16, 2022 11:13:58 GMT

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Post by blork98 on Feb 16, 2022 11:13:58 GMT

Hello,

I have been working through the book slowly and am currently stuck in Chapter 11: Reflection and Refraction. My code is currently able to pass all the tests in Chapter 11. However, when I try to render a scene, Transparent Objects are not rendered Correctly. The transparent sphere is rendered as a solid black sphere.

RefractTransparency.ppm (725.04 KB)

I used the scene description from this thread: forum.raytracerchallenge.com/thread/91/ch-11-reflection-refraction-problem

- add: camera

  width: 300

  height: 300

  field-of-view: 0.45

  from: [ 0, 0, -5 ]

  to: [ 0, 0, 0 ]

  up: [ 0, 1, 0 ]



- add: light

  intensity: [ 0.9, 0.9, 0.9 ]

  at: [ 2, 10, -5 ]



# wall

- add: plane

  transform:

    - [ rotate-x, 1.5708 ]

    - [ translate, 0, 0, 10 ]

  material:

    pattern:

      type: checkers

      colors:

        - [ 0.15, 0.15, 0.15 ]

        - [ 0.85, 0.85, 0.85 ]

    ambient: 0.8

    diffuse: 0.2

    specular: 0



# glass ball

- add: sphere

  material:

    color: [ 1, 1, 1 ]

    ambient: 0

    diffuse: 0

    specular: 0.9

    shininess: 300

    reflective: 0.9

    transparency: 0.9

    refractive-index: 1.5



# hollow center

- add: sphere

  transform:

    - [ scale, 0.5, 0.5, 0.5 ]

  material:

    color: [ 1, 1, 1 ]

    ambient: 0

    diffuse: 0

    specular: 0.9

    shininess: 300

    reflective: 0.9

    transparency: 0.9

    refractive-index: 1.0000034

I even compared my values at pixel (125,125) with the values given in the thread mentioned above and I get the same numbers within 0.0001 at least so am at a loss as where to find the problem.

thanks... its an awesome book by the way

Jamis
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Posts: 310

Chapter 11 - Transparent Objects are not rendered correctly Feb 16, 2022 15:18:01 GMT

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Post by Jamis on Feb 16, 2022 15:18:01 GMT

That's frustrating! I'm glad your tests are all passing, but there's obviously an edge case that I failed to account for in the tests. Hopefully we can figure this out, and in a future edition I can include a few more tests.

Judging from your picture, it looks like reflection is working okay (you can see the reflection around the edges of the sphere). The issue might be with how the transparency is propagated. Does it render any better without the hollow center?

Do you have your source code available online anywhere? I'd be happy to take a look and see if I can find anything that looks off.

blork98
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Posts: 5

Chapter 11 - Transparent Objects are not rendered correctly Feb 17, 2022 0:51:36 GMT

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Post by blork98 on Feb 17, 2022 0:51:36 GMT

Hi Jamis,

thanks for the response.... I am having some trouble logging into GitHub, can I attach a zip file here on this forum?

Reflect seems to be working since I was able to render a scene where it looks ok.

I will try running the scene without the hollow center and post it later tonight. In the office right now.
Let me know if it is possible to attach a zip file with my code, otherwise I will set up a new github tonight.

thanks

Jamis
Administrator

Posts: 310

Chapter 11 - Transparent Objects are not rendered correctly Feb 17, 2022 4:04:26 GMT

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Post by Jamis on Feb 17, 2022 4:04:26 GMT

Sadly, uploading a zip file will probably not work (though you could post it somewhere else online and post a link to it here). GitHub (or similar) is definitely ideal if you can make that work, though.

blork98
New Member

Posts: 5

Chapter 11 - Transparent Objects are not rendered correctly Feb 17, 2022 5:32:27 GMT

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Post by blork98 on Feb 17, 2022 5:32:27 GMT

Hi,

Here is the link for the code I uploaded on GitHub: github.com/blork98/RayTracerChallenge

The shade_hit, reflected_color, refracted_color function are in the Materials.cpp file
while the color_at and intersect_world are in the World.cpp file

The code for rendering the transparent sphere can be found on the Chapter5.cpp file in the void render_refraction_transparency(); function

icolomby
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Posts: 8

Chapter 11 - Transparent Objects are not rendered correctly Feb 17, 2022 18:17:19 GMT Jamis likes this

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Post by icolomby on Feb 17, 2022 18:17:19 GMT

Hi,

Your code is working correctly, however to get the desired result you will need to increase your recursion limit from 1 to 4 or 5. You are not sending enough refracted rays into the scene to generate the proper transparency.

Ian.

blork98
New Member

Posts: 5

Chapter 11 - Transparent Objects are not rendered correctly Feb 18, 2022 10:11:20 GMT

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Post by blork98 on Feb 18, 2022 10:11:20 GMT

Thank you very much Ian, its working now that I set the recursion limit to 5.. I could have sworn I had set the recursion limit to 5 by default...... really careless error on my part.

Btw, are the YAML scene descriptions of the other images in this chapter available? In particular the first picture in chapter 11 and in Chapter 11 page 149 of the pdf edition?

Jamis
Administrator

Posts: 310

Chapter 11 - Transparent Objects are not rendered correctly Feb 18, 2022 17:45:45 GMT

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Post by Jamis on Feb 18, 2022 17:45:45 GMT

Scene descriptions for many (but definitely not anywhere near all) images from the book are scattered around the forum. I really need to go through and organize them into a single place... :/

Here's the scene description for the first image in chapter 11: forum.raytracerchallenge.com/thread/4/reflection-refraction-scene-description

The image on page 149 doesn't seem to have been posted yet. I'll see if I can clean it up and post it later.