{"id":89,"date":"2018-07-22T18:46:10","date_gmt":"2018-07-22T18:46:10","guid":{"rendered":"https:\/\/blogs.scummvm.org\/douglas\/?p=89"},"modified":"2022-05-24T18:49:01","modified_gmt":"2022-05-24T18:49:01","slug":"residualvm-week-10","status":"publish","type":"post","link":"https:\/\/blogs.scummvm.org\/douglas\/2018\/07\/22\/residualvm-week-10\/","title":{"rendered":"ResidualVM: Week 10"},"content":{"rendered":"
And I said: “Let there be shadows!” And there are shadows. Just, not good enough…<\/div>\n
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So, from this week till the end of GSoC I guess I’ll be dealing with OpenGL. As a newbie to computer graphics, I would be lying if I say that I am not worried at all. I once believed that OpenGL hated me, it hated me so much that it didn’t even want me to render a tessellated triangle on the screen. But that hard time is passed now and I am happy that I start to get along well with OpenGL, and it is kind enough to let me produce something physical this week.<\/div>\n
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Ah, the shadow.<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nOkay, shadows. Actually what I have done so far is based on my previous wrong assumption about shadows in\u00a0The Longest Journey<\/i>. In most of the scenes I have played, which is not many actually, characters have\u00a0shadows that look like they are cast from above.\u00a0The Longest Journey<\/i>\u00a0is a 2.5D game with 3D characters and 2D backgrounds, so, in my personal perspective as a CG newbie, it won’t be that intuitive to perform a full shadow casting technique like the Shadow Mapping here. But if shadows are just cast from above, then things are a lot simpler.<\/div>\n
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So, with this “wrong” assumption, and the fact that the original game doesn’t seem to have complex and realistic shadows, I decided to use the simplest shadow casting technique: Planar Shadow. Basically, it just squishes the modal onto a surface and paints it grey. Since I just want to cast the shadow from above, the squishing is even easier. Below is a screenshot when I was testing how I could squish the model.<\/div>\n
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April: I don’t feel so good…<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
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That’s not the whole story. A good shadow should be semi-transparent. But simply enable blending is not enough since transparent faces will cover on each other, and there will be the Z-fighting problem. The solution is intuitive though: stencil test. With the enabling of the stencil test and proper manipulation on the stencil buffer (no two shadow fragments can be drawn on the same location), a nice semi-transparent shadow is produced.<\/div>\n\n\n\n\n
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Blending and Stencil Tet<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n
\nWell, like I said before, this is a wrong assumption.\u00a0The Longest Journey<\/i>\u00a0does compute shadows from existing lights. And there are three types of light in the game: point light, directional light and spotlight. Luckily lights only contribute to the length of the shadow, so right now I think the Planar Shadow technique can still be used.<\/div>\n
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From the look of it right now, I guess it is time for some linear algebra. More updates will come next week.<\/p>\n
All code snippets are generated through\u00a0Carbon<\/a><\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"

And I said: “Let there be shadows!” And there are shadows. Just, not good enough… So, from this week till the end of GSoC I guess I’ll be dealing with OpenGL. As a newbie to computer graphics, I would be lying if I say that I am not worried at all. I once believed that […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[1],"tags":[],"class_list":["post-89","post","type-post","status-publish","format-standard","hentry","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/posts\/89","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/comments?post=89"}],"version-history":[{"count":1,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/posts\/89\/revisions"}],"predecessor-version":[{"id":90,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/posts\/89\/revisions\/90"}],"wp:attachment":[{"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/media?parent=89"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/categories?post=89"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blogs.scummvm.org\/douglas\/wp-json\/wp\/v2\/tags?post=89"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}