tests: Add uv to tangent lengths test

tests/CMakeLists.txt

@@ -37,7 +37,7 @@ if(XRT_HAVE_D3D12)
 	list(APPEND tests tests_comp_client_d3d12)
 endif()
 if(XRT_HAVE_VULKAN)
-	list(APPEND tests tests_comp_client_vulkan)
+	list(APPEND tests tests_comp_client_vulkan tests_uv_to_tangent)
 endif()
 if(XRT_HAVE_OPENGL
    AND XRT_HAVE_OPENGL_GLX
@@ -101,6 +101,7 @@ if(XRT_HAVE_VULKAN)
 	target_link_libraries(
 		tests_comp_client_vulkan PRIVATE comp_client comp_mock comp_util aux_vk
 		)
+	target_link_libraries(tests_uv_to_tangent PRIVATE comp_render)
 endif()
 
 if(_have_opengl_test)

tests/tests_uv_to_tangent.cpp

@@ -0,0 +1,111 @@
+// Copyright 2023, Collabora, Ltd.
+// SPDX-License-Identifier: BSL-1.0
+/*!
+ * @file
+ * @brief Testing UV to tangent values.
+ * @author Jakob Bornecrantz <jakob@collabora.com>
+ */
+
+#include "catch/catch.hpp"
+
+#include "math/m_mathinclude.h"
+#include "render/render_interface.h"
+
+
+#define QUARTER_PI (M_PI / 4)
+#define SIXTH_PI (M_PI / 6)
+#define MARGIN (0.000001)
+
+static inline xrt_normalized_rect
+rect(float x, float y, float w, float h)
+{
+	xrt_normalized_rect rect = {x, y, w, h};
+	return rect;
+}
+
+static inline void
+check(xrt_normalized_rect &result, xrt_normalized_rect &&truth)
+{
+	REQUIRE_THAT(result.x, Catch::WithinAbs(truth.x, MARGIN));
+	REQUIRE_THAT(result.y, Catch::WithinAbs(truth.y, MARGIN));
+	REQUIRE_THAT(result.w, Catch::WithinAbs(truth.w, MARGIN));
+	REQUIRE_THAT(result.h, Catch::WithinAbs(truth.h, MARGIN));
+}
+
+#define CAPUTER_FOV(FOV) CAPTURE(FOV.angle_up, FOV.angle_down, FOV.angle_left, FOV.angle_right);
+
+
+TEST_CASE("render_calc_uv_to_tangent_lengths_rect")
+{
+	// Sanity check.
+	REQUIRE_THAT(tan(QUARTER_PI), Catch::WithinAbs(1.0, MARGIN));
+
+	SECTION("45_degrees")
+	{
+		struct xrt_fov f45 = XRT_STRUCT_INIT;
+		f45.angle_down = -QUARTER_PI;
+		f45.angle_up = QUARTER_PI;
+		f45.angle_left = -QUARTER_PI;
+		f45.angle_right = QUARTER_PI;
+
+		SECTION("normal")
+		{
+			CAPTURE(f45.angle_up, f45.angle_down, f45.angle_left, f45.angle_right);
+			struct xrt_normalized_rect result;
+			render_calc_uv_to_tangent_lengths_rect(&f45, &result);
+
+			/*
+			 * We expect a fov of 45 degrees in all angles to have tangets
+			 * of 1 or -1. In order to transform uv [0 .. 1] to [-1 .. 1]
+			 * we need to have a width of 2 and a offset of -1.
+			 */
+			check(result, rect(-1, -1, 2, 2));
+		}
+
+		SECTION("flipped_vertical")
+		{
+			f45.angle_down = -f45.angle_down;
+			f45.angle_up = -f45.angle_up;
+
+			CAPUTER_FOV(f45);
+			struct xrt_normalized_rect result;
+			render_calc_uv_to_tangent_lengths_rect(&f45, &result);
+
+			// We expect the same values as normal but with y and h negated.
+			check(result, rect(-1, 1, 2, -2));
+		}
+
+		SECTION("flipped_horizontal")
+		{
+			f45.angle_left = -f45.angle_left;
+			f45.angle_right = -f45.angle_right;
+
+			CAPUTER_FOV(f45);
+			struct xrt_normalized_rect result;
+			render_calc_uv_to_tangent_lengths_rect(&f45, &result);
+
+			// We expect the same values as normal but with x and w negated.
+			check(result, rect(1, -1, -2, 2));
+		}
+	}
+
+
+	SECTION("30_degrees")
+	{
+		struct xrt_fov f30 = XRT_STRUCT_INIT;
+		f30.angle_down = -SIXTH_PI;
+		f30.angle_up = SIXTH_PI;
+		f30.angle_left = -SIXTH_PI;
+		f30.angle_right = SIXTH_PI;
+
+		CAPUTER_FOV(f30);
+		struct xrt_normalized_rect result;
+		render_calc_uv_to_tangent_lengths_rect(&f30, &result);
+
+		float t = tan(SIXTH_PI);
+		float t2 = t * 2;
+
+		// We expect the offset to be -tan(PI/6) and the lengths to be tan(PI/6) * 2.
+		check(result, rect(-t, -t, t2, t2));
+	}
+}