Alpha Blending Multiple Render Targets | Handmade Hero Episode Guide

1:06Run the game and show our current situation with render targets

2:56handmade_entity.cpp: Make UpdateAndRenderEntities() create two different ClipRects for the alpha and normal floors

6:08Run the game and see that the alpha stuff is gone

6:53Consider ways of using multiple render targets

9:28handmade_render.cpp: Add a RenderGroupEntryType_blend_render_target in RenderCommandsToBitmap() and introduce BlendRenderTarget()

14:36handmade_render.cpp: Implement BlendRenderTarget() based on DrawRectangle()

24:44handmade_render.cpp: Introduce Pack4x8()

26:00handmade_render.cpp: Continue implementing BlendRenderTarget(), making it do gamma properly

27:27handmade_render_group.h: Add RenderGroupEntryType_blend_render_target to the render_group_entry_type enum and introduce render_entry_blend_render_target struct

29:14Run the game and see that it does nothing

29:33handmade_render.cpp: Make RenderCommandsToBitmap() clear everyone

31:55handmade_render_group.cpp: Introduce PushBlendRenderTarget() based on PushClipRect(), which will do the composite

39:39handmade_entity.cpp: Make UpdateAndRenderEntities() call PushBlendRenderTarget()

41:30Debugger: Run the game and crash in Win32CompleteAllWork()

41:51build.bat: Switch to -Od, run the game and crash in BlendRenderTarget()

42:33handmade_entity.cpp: Make UpdateAndRenderEntities() use AlphaFloorRenderTarget and pass it to BlendRenderTarget()

43:07build.bat: Switch to -O2, run the game and see how slowly the game now runs

44:16Debugger: Step through BlendRenderTarget() and investigate what's happening

44:51handmade_render.cpp: Make BlendRenderTarget() correctly set the DestColor and Result

45:32Run the game, see no alpha blending happening and investigate why

46:40handmade_render.cpp: Try making BlendRenderTarget() hardcode the Alpha to 0.5f

46:57Run the game and see that the Alpha is not taking effect

48:01build.bat: Switch to -Od, step in to BlendRenderTarget() and see what happens when we have a source pixel with something in it

49:23handmade_entity.cpp: Remove the transient_clip_rect from UpdateAndRenderEntities() and make it manually set the CurrentClipRect

50:12Run the game and see the prettiness before switching to -O2

50:45Run the game and marvel at the indescribable cacophony of epileptic color^α

51:36handmade_render.cpp: Make BlendRenderTarget() use SRGB255ToLinear1() and Linear1ToSRGB255()

53:51Run the game and again see the sparkly

54:11handmade_render.cpp: Prevent Pack4x8() from doing the multiply

54:31Run the game and see that we're getting closer to being correct

54:47handmade_render.cpp: Make BlendRenderTarget() use the correct Alpha

56:18handmade_entity.cpp: Make UpdateAndRenderEntities() set TestAlpha as a single r32 rather than an array of them

58:40"I love how it can't ever tell you any values in release mode"^β

58:46Debugger: Step into UpdateAndRenderEntities() and investigate how TestAlpha got to be set to 1.0f

1:01:42handmade_entity.cpp: Make UpdateAndRenderEntities() pass FadeTopEndZ and FadeTopStartZ to TestAlpha() in the opposite order

1:01:58build.bat: Switch to -O2, run the game and see the alpha blending working beautifully

1:03:12handmade_render.cpp: Make RenderCommandsToBitmap() clear both the MaxRenderTargetIndex and the previous TargetIndex

1:03:41Run the game and see that now it looks like we're good

1:04:00Note that the clear is clearing at 1.0f alpha, and that it has to actually clear, not blend

1:04:46Q&A

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1:04:46Q&A

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1:04:46Q&A

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1:05:57Kknewkles Giger / Lovecraft-themed Handmade Hero DLC confirmed?

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1:05:57Kknewkles Giger / Lovecraft-themed Handmade Hero DLC confirmed?

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1:05:57Kknewkles Giger / Lovecraft-themed Handmade Hero DLC confirmed?

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1:06:08soysaucethekid Are you writing to the second buffer all the time? If so, is it possible to only use when you need it (like during the transitions)?

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1:06:08soysaucethekid Are you writing to the second buffer all the time? If so, is it possible to only use when you need it (like during the transitions)?

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1:06:08soysaucethekid Are you writing to the second buffer all the time? If so, is it possible to only use when you need it (like during the transitions)?

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1:06:37handmade_entity.cpp: Make UpdateAndRenderEntities() only do the multiple buffers stuff if the alpha is enabled

1:09:25pseudonym73 How does a limbless child "limp along", exactly?

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1:09:25pseudonym73 How does a limbless child "limp along", exactly?

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1:09:25pseudonym73 How does a limbless child "limp along", exactly?

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1:09:34inquarry How many floors can this code support? I envision a tall tower or stairwell, peering down 20 or so floors and seeing NPCs acting as normal. Was that your intent?

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1:09:34inquarry How many floors can this code support? I envision a tall tower or stairwell, peering down 20 or so floors and seeing NPCs acting as normal. Was that your intent?

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1:09:34inquarry How many floors can this code support? I envision a tall tower or stairwell, peering down 20 or so floors and seeing NPCs acting as normal. Was that your intent?

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1:10:56Kknewkles How do you use trace files to debug? Someone trying my game prototype had a crash and sent me a (95MB) dump file, since you once said it's helpful. I don't doubt that, but what do you do with the damn thing?

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1:10:56Kknewkles How do you use trace files to debug? Someone trying my game prototype had a crash and sent me a (95MB) dump file, since you once said it's helpful. I don't doubt that, but what do you do with the damn thing?

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1:10:56Kknewkles How do you use trace files to debug? Someone trying my game prototype had a crash and sent me a (95MB) dump file, since you once said it's helpful. I don't doubt that, but what do you do with the damn thing?

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1:13:39Wrap it up

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1:13:39Wrap it up

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1:13:39Wrap it up

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