Enabling the OpenGL Depth Buffer — Handmade Hero — Episode Guide

1:32Run the game, recap and set the stage for the day

4:55Blackboard: Using the Z-buffer to sort ground tiles

6:35Blackboard: Slanting the upright sprites to make them occlude each other properly

13:55Run the game and illustrate why this scheme will be important for debugging purposes

14:08"We're going to write some code and hope that it's right"^α

14:56Determine to turn on the Z-buffer¹

15:36handmade_opengl.cpp: Make OpenGLRenderCommands() enable GL_DEPTH_TEST and call glDepthMask()² and glColorMask()

21:40win32_handmade.cpp: Make Win32SetPixelFormat() set cDepthBits³

25:00win32_handmade.cpp: Make Win32SetPixelFormat() specify the colour bits⁴

28:39Run the game, see nothing on the screen and investigate why

29:24handmade_opengl.cpp: Make OpenGLRenderCommands() pass GL_DEPTH_BUFFER_BIT to glClear()

31:56Run the game to see that we're getting Z-tested drawing

32:42Blackboard: Preventing fully transparent pixels from entering the Z-buffer

36:25handmade_opengl.cpp: Make OpenGLRenderCommands() enable and call glAlphaFunc()⁵

38:24handmade_opengl.cpp: Temporarily make glAlphaFunc() operate for alpha values greater than 0

39:04Blackboard: No blending if sprites happen to be drawn in the wrong order

42:06handmade_opengl.cpp: Make OpenGLRenderCommands() call glDepthFunc()⁶

43:19Run the game to see that the drawing order is being respected, but that the sort is unstable

46:05Determine to process the Z-values⁷

50:46Blackboard: Near and Far Clip (Planes)

53:50Blackboard: Mapping the Z-values in the correct direction to the -1 to 1 range

56:27Blackboard: Determining the structure of the mapping function

59:08Blackboard: Solve these equations for a and b

1:02:11Blackboard: Verify these equations

1:08:49Blackboard: Solve the equations again, passing in the correct values

1:17:44handmade_math.h: Make PerspectiveProjection() compute d and e to pass to the matrix

1:19:02Run the game to see the finer grained Z-fighting

1:20:03handmade_render_group.cpp: Enable PushBitmap() to increase the sprites' height relative to their Z

1:22:52Run the game to see the slanted sprites, and consider why we must take the camera into account for shearing

1:25:03handmade_render_group.cpp: Make PushBitmap() also modify the sprites' Y and X values

1:27:21Consider using the camera's relative position to compute these modifications

1:28:48Q&A

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1:28:48Q&A

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1:28:48Q&A

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1:29:20ratchetfreak When adjusting the sprite like that, don't you need to interpolate the texture coordinates in screenspace instead of clipspace (the default)?

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1:29:20ratchetfreak When adjusting the sprite like that, don't you need to interpolate the texture coordinates in screenspace instead of clipspace (the default)?

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1:29:20ratchetfreak When adjusting the sprite like that, don't you need to interpolate the texture coordinates in screenspace instead of clipspace (the default)?

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1:30:29macielda What is Alpha to Coverage? Any good references on that?

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1:30:29macielda What is Alpha to Coverage? Any good references on that?

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1:30:29macielda What is Alpha to Coverage? Any good references on that?

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1:31:48k1ng_k3v1n Would an orthogonal projection matrix be applicable for your game?

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1:31:48k1ng_k3v1n Would an orthogonal projection matrix be applicable for your game?

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1:31:48k1ng_k3v1n Would an orthogonal projection matrix be applicable for your game?

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1:32:19sharlock93 Is the -n and -f because OpenGL has the camera on the negative -z?

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1:32:19sharlock93 Is the -n and -f because OpenGL has the camera on the negative -z?

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1:32:19sharlock93 Is the -n and -f because OpenGL has the camera on the negative -z?

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1:33:06magik603 Why are you using legacy OpenGL?

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1:33:06magik603 Why are you using legacy OpenGL?

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1:33:06magik603 Why are you using legacy OpenGL?

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1:34:49cvaucher Do you typically use an infinite far plane for increased precision? Shawn McGrath mentioned it in his stream awhile back

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1:34:49cvaucher Do you typically use an infinite far plane for increased precision? Shawn McGrath mentioned it in his stream awhile back

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1:34:49cvaucher Do you typically use an infinite far plane for increased precision? Shawn McGrath mentioned it in his stream awhile back

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1:36:20macielda Would it be simpler to use Orthographic transforms for upright objects? Are you not simply undoing the Perspective Projection there?

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1:36:20macielda Would it be simpler to use Orthographic transforms for upright objects? Are you not simply undoing the Perspective Projection there?

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1:36:20macielda Would it be simpler to use Orthographic transforms for upright objects? Are you not simply undoing the Perspective Projection there?

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1:37:28pepevel Would it be possible to use a shader to do the Z-buffer rendering?

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1:37:28pepevel Would it be possible to use a shader to do the Z-buffer rendering?

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1:37:28pepevel Would it be possible to use a shader to do the Z-buffer rendering?

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1:40:17sharlock93 So the near and far plane are linearly mapped. I have read somewhere where the mapping is not linear, in which case do we not make them linear?

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1:40:17sharlock93 So the near and far plane are linearly mapped. I have read somewhere where the mapping is not linear, in which case do we not make them linear?

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1:40:17sharlock93 So the near and far plane are linearly mapped. I have read somewhere where the mapping is not linear, in which case do we not make them linear?

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1:43:13Blackboard: Accounting for the -z in our coefficients

1:48:15Consult the OpenGL spec⁸

1:52:24sharlock93 Oh yeah, sorry, I mixed two things up

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1:52:24sharlock93 Oh yeah, sorry, I mixed two things up

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1:52:24sharlock93 Oh yeah, sorry, I mixed two things up

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1:52:34Blackboard: Computing a and b, accounting for the -z

2:02:30handmade_math.h: Try to make PerspectiveProjection() compute the non-perspective corrected terms for orthographic

2:05:23End it there

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2:05:23End it there

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2:05:23End it there

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