rdm
New Member
Posts: 4
|
Post by rdm on Apr 18, 2019 7:57:53 GMT
Hi all! Could someone help me with something that's bugging me about Chapter 7 assignment? Even using the same recipe of the book my image is quite brighter than the one on the book (cf. attachment)!  I thought the image in the book could serve as a reference (it could be a nice extra content by the way, unless the author already uploaded reference images somewhere and I just missed them...  ). Is this supposed to happen, or is my renderer off somehow? It would be strange with all the tests green, but still... Mind you, I'm not expecting a solution, I'll do my homework if the case: but I'd really like to know whether I'm going on a goose chase so I can move on. Oh, and not less important: thanks Jamis for the wonderful book! I do TDD both at work and in my own project already, but seeing someone's else take on it, and doing that on image data is proving a great ride so far. Thank you! Riccardo  |
|
|
|
Post by Jamis on Apr 18, 2019 12:22:22 GMT
Hello Riccardo, I think your image looks exactly right. (Congrats!) I've attached the render used in the book so you can compare. The images in the print version of the book all turned out significantly darker than the digital version. (I have to admit, I'm kind of disappointed about the colors in the print version of the book.) If you ever would like me to post a reference image, just let me know! - Jamis Attachments:
|
|
rdm
New Member
Posts: 4
|
Post by rdm on Apr 18, 2019 12:45:44 GMT
Thank you for the very prompt answer, Jamis! Weird that the book images are so darker in the digital version: I expected this kind of issues only when ink and paper are involved, but it's not that important (the darker images do look good, though!). If it's just for me, don't bother about the reference images, really: I thought it was a neat idea to complement the tests, but as far as I'm concerned I'm fine now. Onward to chapter 8, then!  Cheers, Riccardo PS: looking forward to finishing your "Mazes for programmers": I had to interrupt it because it was too good and tinkering with mazes was consuming all my spare time (which is a big plus of "Ray Tracer Challenge": there are set objectives pulling you forward). |
|
|
|
Post by ascotti on Apr 19, 2019 21:23:43 GMT
Maybe it's related to gamma correction? The renderer works in linear color space and if the output images are not corrected they will display darker and "constrasty" (on a monitor too). Same is true for "imported" colors BTW, image textures or e.g. CSS RGB values need to be converted to linear space or they won't look right in the renderer.
|
|
rdm
New Member
Posts: 4
|
Post by rdm on Apr 24, 2019 12:48:22 GMT
I confess my ignorance on the topic RGB vs sRGB topic.
The issue, in this case, is that the images generated by the renderer look brighter than the one on the book, but still color profiles could be something to look into.
Thank you
|
|
|
|
Post by krotus on Apr 2, 2020 3:01:08 GMT
FYI, as a very experienced graphic designer, the reason the images in the book are darker is likely the conversion from RGB (which is mixed with light) to CYMK (which is mixed with pigments). Try opening your rendered image in an image editor and change the color space to from RGB to CMYK and see what happens.
It's a very common issue in graphic design because there is no exact color conversion from RGB to CMYK.
|
|
|
|
Post by trejkaz on Jul 6, 2021 20:55:45 GMT
Maybe it's related to gamma correction? The renderer works in linear color space and if the output images are not corrected they will display darker and "constrasty" (on a monitor too). Same is true for "imported" colors BTW, image textures or e.g. CSS RGB values need to be converted to linear space or they won't look right in the renderer. I had been wondering about this too, so I went digging for specs for the PPM file format, and as far as I can tell, PPM files are non-linear as well. So all the test cases for reading and writing PPM files are wrong? |
|
).
