The open source OpenXR runtime
c/render: Expose uv to tangent lengths function
Also document it better.
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-37
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src/xrt/compositor/render/render_distortion.c
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-37
src/xrt/compositor/render/render_distortion.c
···
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struct xrt_vec2 scale;
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};
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static void
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calc_uv_to_tanangle(struct xrt_device *xdev, uint32_t view, struct xrt_normalized_rect *out_rect)
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{
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const struct xrt_fov fov = xdev->hmd->distortion.fov[view];
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const double tan_left = tan(fov.angle_left);
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const double tan_right = tan(fov.angle_right);
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const double tan_down = tan(fov.angle_down);
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const double tan_up = tan(fov.angle_up);
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const double tan_width = tan_right - tan_left;
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const double tan_height = tan_up - tan_down;
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/*
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* I do not know why we have to calculate the offsets like this, but
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* this one is the one that seems to work with what is currently in the
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* calc timewarp matrix function and the distortion shader. It works
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* with Index (unbalanced left and right angles) and WMR (unbalanced up
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* and down angles) so here it is. In so far it matches what the gfx
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* and non-timewarp compute pipeline produces.
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*/
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const double tan_offset_x = ((tan_right + tan_left) - tan_width) / 2;
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const double tan_offset_y = (-(tan_up + tan_down) - tan_height) / 2;
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struct xrt_normalized_rect transform = {
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.x = (float)tan_offset_x,
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.y = (float)tan_offset_y,
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.w = (float)tan_width,
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.h = (float)tan_height,
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};
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*out_rect = transform;
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}
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XRT_CHECK_RESULT static VkResult
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create_and_fill_in_distortion_buffer_for_view(struct vk_bundle *vk,
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struct xrt_device *xdev,
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static_assert(RENDER_DISTORTION_NUM_IMAGES == 6, "Wrong number of distortion images!");
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calc_uv_to_tanangle(xdev, 0, &r->distortion.uv_to_tanangle[0]);
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calc_uv_to_tanangle(xdev, 1, &r->distortion.uv_to_tanangle[1]);
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render_calc_uv_to_tangent_lengths_rect(&xdev->hmd->distortion.fov[0], &r->distortion.uv_to_tanangle[0]);
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render_calc_uv_to_tangent_lengths_rect(&xdev->hmd->distortion.fov[1], &r->distortion.uv_to_tanangle[1]);
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/*
+18
src/xrt/compositor/render/render_interface.h
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src/xrt/compositor/render/render_interface.h
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const struct xrt_pose *new_pose,
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struct xrt_matrix_4x4 *matrix);
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/*!
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* This function constructs a transformation in the form of a normalized rect
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* that lets you go from a UV coordinate on a projection plane to the a point on
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* the tangent plane. An example is that the UV coordinate `(0, 0)` would be
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* transformed to `(tan(angle_left), tan(fov.angle_up))`. The tangent plane (aka
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* tangent space) is really the tangent of the angle, aka length at unit distance.
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*
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* For the trivial case of an fov with 45 degrees angles, that is where the
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* tangent length are `1` (aka `tan(45)`), the transformation would go from
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* `[0 .. 1]` to `[-1 .. 1]` the expected returns are `x = -1`, `y = -1`,
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* `w = 2` and `h = 2`.
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*
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* param fov The fov of the projection image.
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* param[out] out_rect Transformation from UV to tangent lengths.
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*/
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void
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render_calc_uv_to_tangent_lengths_rect(const struct xrt_fov *fov, struct xrt_normalized_rect *out_rect);
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/*
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*
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src/xrt/compositor/render/render_util.c
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src/xrt/compositor/render/render_util.c
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#endif
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}
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/*
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*
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* 'Exported' functions.
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*
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*/
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void
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render_calc_time_warp_matrix(const struct xrt_pose *src_pose,
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const struct xrt_fov *src_fov,
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matrix->v[i] = (float)result.v[i];
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}
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}
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void
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render_calc_uv_to_tangent_lengths_rect(const struct xrt_fov *fov, struct xrt_normalized_rect *out_rect)
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{
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const struct xrt_fov copy = *fov;
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const double tan_left = tan(copy.angle_left);
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const double tan_right = tan(copy.angle_right);
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const double tan_down = tan(copy.angle_down);
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const double tan_up = tan(copy.angle_up);
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const double tan_width = tan_right - tan_left;
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const double tan_height = tan_up - tan_down;
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/*
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* I do not know why we have to calculate the offsets like this, but
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* this one is the one that seems to work with what is currently in the
143
+
* calc timewarp matrix function and the distortion shader. It works
144
+
* with Index (unbalanced left and right angles) and WMR (unbalanced up
145
+
* and down angles) so here it is. In so far it matches what the gfx
146
+
* and non-timewarp compute pipeline produces.
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*/
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const double tan_offset_x = ((tan_right + tan_left) - tan_width) / 2;
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const double tan_offset_y = (-(tan_up + tan_down) - tan_height) / 2;
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struct xrt_normalized_rect transform = {
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.x = (float)tan_offset_x,
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.y = (float)tan_offset_y,
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.w = (float)tan_width,
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.h = (float)tan_height,
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};
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*out_rect = transform;
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}