GPU: Fix Issue with recursive downsample and Intel HDXXX

This is caused by a driver bug that prevent us from rendering to (or even
binding) a texture mip level that is below GL_TEXTURE_MAX_LEVEL of the
target texture. This is fine in most drivers (and legal AFAIK) but not on
thoses Intels HDXXX + Windows.

As a fix we just put GL_TEXTURE_MAX_LEVEL lower (which is illegal because
it is undefined behaviour), but in practice it works ok and does not
trigger any warnings or errors.

This commit fixes most of the problems encountered on these GPUs (T56668).

1 files changed, 18 insertions, 7 deletions

diff --git a/source/blender/gpu/intern/gpu_texture.c b/source/blender/gpu/intern/gpu_texture.c
index 6a8e686afb3..c3a1148a360 100644
--- a/source/blender/gpu/intern/gpu_texture.c
+++ b/source/blender/gpu/intern/gpu_texture.c
@@ -916,12 +916,13 @@ GPUTexture *GPU_texture_create_cube(
 	const int channels = gpu_get_component_count(tex_format);
 
 	if (fpixels) {
-		fpixels_px = fpixels + 0 * w * w * channels;
-		fpixels_nx = fpixels + 1 * w * w * channels;
-		fpixels_py = fpixels + 2 * w * w * channels;
-		fpixels_ny = fpixels + 3 * w * w * channels;
-		fpixels_pz = fpixels + 4 * w * w * channels;
-		fpixels_nz = fpixels + 5 * w * w * channels;
+		int face_ofs = w * w * channels;
+		fpixels_px = fpixels + 0 * face_ofs;
+		fpixels_nx = fpixels + 1 * face_ofs;
+		fpixels_py = fpixels + 2 * face_ofs;
+		fpixels_ny = fpixels + 3 * face_ofs;
+		fpixels_pz = fpixels + 4 * face_ofs;
+		fpixels_nz = fpixels + 5 * face_ofs;
 	}
 	else {
 		fpixels_px = fpixels_py = fpixels_pz = fpixels_nx = fpixels_ny = fpixels_nz = NULL;
@@ -1099,6 +1100,7 @@ void *GPU_texture_read(GPUTexture *tex, GPUDataFormat gpu_data_format, int miplv
 	samples_count *= size[0];
 	samples_count *= max_ii(1, size[1]);
 	samples_count *= max_ii(1, size[2]);
+	samples_count *= (GPU_texture_cube(tex)) ? 6 : 1;
 
 	switch (gpu_data_format) {
 		case GPU_DATA_FLOAT:
@@ -1123,7 +1125,16 @@ void *GPU_texture_read(GPUTexture *tex, GPUDataFormat gpu_data_format, int miplv
 
 	glBindTexture(tex->target, tex->bindcode);
 
-	glGetTexImage(tex->target, miplvl, data_format, data_type, buf);
+	if (GPU_texture_cube(tex)) {
+		int cube_face_size = buf_size / 6;
+		for (int i = 0; i < 6; ++i) {
+			glGetTexImage(GL_TEXTURE_CUBE_MAP_POSITIVE_X + i, miplvl, data_format, data_type,
+			              ((char *)buf) + cube_face_size * i);
+		}
+	}
+	else {
+		glGetTexImage(tex->target, miplvl, data_format, data_type, buf);
+	}
 
 	glBindTexture(tex->target, 0);