LightmapRenderer.renderLightMap() is tad too slow

[curioustorvald]

Can be mitigated by updating only on every other frame (frameskip of 2 is too slow for fast-moving player). Old mini-tile smoothing can be replaced with blocky render with blur shader.

[curioustorvald]

Calculation is the one slows things a lot; need to test all the recent commits on less powerful PC.

[curioustorvald]

~41 fps on my macbookpro 9,2; shader is running very efficiently -- no boost even if smoothing is disabled.

[curioustorvald]

Can't get the lightmap downsampling to work -- weird horizontal lines all over

[curioustorvald]

With fixing camera position at integer numbers, downsampling only works when the screen is NOT resized.

[curioustorvald]

Was able to achieve downsampling w/o texture issue (keeping default LINEAR filter was the culprit, fixed with NEAREST), now camera-related choppiness is an issue. Fortunately, downsample factor of 2 is not noticeable when blurring is turned on, so I'd settle there.

[curioustorvald]

Tricks applied so far:

• Old blocky rendering (coalesces same-level blocks as one long block) with shader-powered blur
• Lightmap downsampled by 2
• Update lightmap on every other frame

[curioustorvald]

New idea: at least we can make drawing faster using fragment shader to make the GPU tile itself, and while you're at it, also apply it to the block drawing.

[curioustorvald]

Lightmap is now fully downsampled, no need to draw blocks in a naive way -- just draw px on pixmap.

Update lightmap on every other frame is now ditched, will produce "jitter" when the camera moves.

One last question: Can we make it faster by calculating the lightmap on GPU using Fragment Shader?

[curioustorvald]

Further optimisation was done by memoising the result of DynamicLumFunction every frame to cut down the unnecessary function calls caused by torches.

[curioustorvald]

See branch "NEWLIGHT2"