light: Add support for LIGHTING_E5BGR9.

[dsvensson]

Forward port/adaptation of Spike's work in https://github.com/ericwa/ericw-tools/pull/280 and not really fit for merging. Proposing it as draft in hope of getting help to figure out what needs to be done to get it into a mergable state.

The output of these lightmaps is supported by FTE, QSS, QSS-M.

The primary usecase is HDR and iris adaptation that alters the brightness between scenes with a delay of going from outdoors to indoors, but it also reduces banding due to the float nature. From a multiplayer perspective it allows for kicking up the brightness without lightmaps turning into pure garbage.

[ericwa]

Thanks for resurrecting this.

I think it's pretty close to good to merge, I've got a small docs update:

diff --git a/docs/light.rst b/docs/light.rst
index 2454c6c3..810ce0e2 100644
--- a/docs/light.rst
+++ b/docs/light.rst
@@ -315,6 +315,14 @@ Experimental options

    Writes lux data into the bsp itself.

+.. option:: -hdr
+
+   Write .lit file with e5bgr9 data.
+
+.. option:: -bspxhdr
+
+   Writes LIGHTING_E5BGR9 bspx lump.
+
 .. option:: -lmscale n

    Equivalent to "_lightmap_scale" worldspawn key.
diff --git a/light/light.cc b/light/light.cc
index 71a4bf14..fbb6edae 100644
--- a/light/light.cc
+++ b/light/light.cc
@@ -322,7 +322,7 @@ light_settings::light_settings()
           "writes lux data into the bsp itself"},
       hdr{this, "hdr", [&](source) { write_litfile |= lightfile::external; write_litfile |= lightfile::hdr; }, &experimental_group, "write .lit file with e5bgr9 data"},
       bspxhdr{this, "bspxhdr", [&](source) { write_litfile |= lightfile::bspx; write_litfile |= lightfile::hdr; }, &experimental_group,
-          "writes lux data into the bsp itself"},
+          "writes LIGHTING_E5BGR9 bspx lump"},
       bspxonly{this, "bspxonly",
           [&](source source) {
               write_litfile = lightfile::bspx;

I'd like to add a test or two that lights a map with -bspxhdr and then e5rgb9 sample back to a float, we have similar tests for decouple LM, regular Q1 .lit, Q2 vanilla lightmaps, etc.

I should also credit Spike in the final merge commit for the initial patch.

[ericwa]

I'm doing the last batch of changes I wanted to add to this in my branch https://github.com/ericwa/ericw-tools/tree/hdr

• [x] add a HDR_UnpackE5BRG9 decode function (uint32_t -> qvec3f)
• [x] tests for HDR_PackE5BRG9 + HDR_UnpackE5BRG9
• [x] rework HDR_PackE5BRG9 implementation to match opengl spec
• [x] lightpreview - add brightness slider
• [x] lightpreview - load + render
  • [x] for .lit hdr format
  • [x] for hdr bspx format
• [x] add an end-to-end test
  • [x] for .lit hdr format
  • [x] for hdr bspx format
• [x] final check in QSS/FTE that they have the expected appearance in game, match the appearance of vanilla lightmaps within the [0,255] range
  • [x] for .lit hdr format
  • [x] for hdr bspx format

I'll hopefully wrap this up soon + merge!

[dsvensson]

Thank you so much for picking this up. Was about to return to this after focusing on another project for the past few weeks. Your improvements look much better than what I would have been able to pull off. 🙏

[ericwa]

Merged this in https://github.com/ericwa/ericw-tools/commit/30868eacb7412a82b6aaa38950afbac1b3c36418