GPUFramebuffer: Fix wrong stencil clearing

source/blender/draw/engines/eevee/eevee_engine.c

@@ -198,7 +198,7 @@ static void eevee_draw_background(void *vedata)
 	while (loop_len--) {
 		float clear_col[4] = {0.0f, 0.0f, 0.0f, 0.0f};
 		float clear_depth = 1.0f;
-		uint clear_stencil = 0xFF;
+		uint clear_stencil = 0x0;
 		uint primes[3] = {2, 3, 7};
 		double offset[3] = {0.0, 0.0, 0.0};
 		double r[3];

source/blender/draw/engines/eevee/eevee_render.c

@@ -466,7 +466,7 @@ void EEVEE_render_draw(EEVEE_Data *vedata, RenderEngine *engine, RenderLayer *rl
 	while (render_samples < tot_sample && !RE_engine_test_break(engine)) {
 		float clear_col[4] = {0.0f, 0.0f, 0.0f, 0.0f};
 		float clear_depth = 1.0f;
-		uint clear_stencil = 0xFF;
+		uint clear_stencil = 0x00;
 		uint primes[3] = {2, 3, 7};
 		double offset[3] = {0.0, 0.0, 0.0};
 		double r[3];

source/blender/draw/engines/workbench/workbench_deferred.c

@@ -861,7 +861,7 @@ void workbench_deferred_draw_background(WORKBENCH_Data *vedata)
 	WORKBENCH_PrivateData *wpd = stl->g_data;
 	const float clear_depth = 1.0f;
 	const float clear_color[4] = {0.0f, 0.0f, 0.0f, 0.0f};
-	uint clear_stencil = 0xFF;
+	uint clear_stencil = 0x00;
 
 	DRW_stats_group_start("Clear Background");
 	GPU_framebuffer_bind(fbl->prepass_fb);

source/blender/gpu/intern/gpu_framebuffer.c

@@ -500,7 +500,8 @@ void GPU_framebuffer_clear(
 		glClearDepth(clear_depth);
 	}
 	if (buffers & GPU_STENCIL_BIT) {
-		glStencilMask(clear_stencil);
+		glStencilMask(0xFF);
+		glClearStencil(clear_stencil);
 	}
 
 	GLbitfield mask = convert_buffer_bits_to_gl(buffers);