[vlc-devel] [PATCH 12/16] opengl: apply stereo transform using a matrix
Romain Vimont
rom1v at videolabs.io
Tue Mar 17 17:26:45 CET 2020
The multiview mode (stereo) was applied by changing the texture
paddings to crop only the left eye.
The problem is that these texture paddings are specific to the input
picture, while the stereo mode is specific to the renderer, which should
be independent of the input picture.
To separate these concerns, apply the stereo mode using a matrix to
transform the texture coordinates from the renderer.
---
modules/video_output/opengl/renderer.c | 137 +++++++++++++++----------
modules/video_output/opengl/renderer.h | 2 +
2 files changed, 84 insertions(+), 55 deletions(-)
diff --git a/modules/video_output/opengl/renderer.c b/modules/video_output/opengl/renderer.c
index 6d90e7ebcb..a3703a7e7b 100644
--- a/modules/video_output/opengl/renderer.c
+++ b/modules/video_output/opengl/renderer.c
@@ -169,6 +169,81 @@ static void getOrientationTransformMatrix(video_orientation_t orientation,
}
}
+static void
+InitStereoMatrix(GLfloat matrix_out[static 3*3],
+ video_multiview_mode_t multiview_mode)
+{
+ /*
+ * The stereo matrix transforms 2D pictures coordinates to crop the
+ * content, in order to view only one eye.
+ *
+ * This 2D transformation is affine, so the matrix is 3x3 and applies to 3D
+ * vectors in the form (x, y, 1).
+ *
+ * Note that since for now, we always crop the left eye, in practice the
+ * offset is always 0, so the transform is actually linear (a 2x2 matrix
+ * would be sufficient).
+ */
+
+#define COL(x) (x*3)
+#define ROW(x) (x)
+
+ /* Initialize to identity 3x3 */
+ memset(matrix_out, 0, 3 * 3 * sizeof(float));
+ matrix_out[COL(0) + ROW(0)] = 1;
+ matrix_out[COL(1) + ROW(1)] = 1;
+ matrix_out[COL(2) + ROW(2)] = 1;
+
+ switch (multiview_mode)
+ {
+ case MULTIVIEW_STEREO_SBS:
+ /*
+ * +----------+----------+
+ * | . |
+ * | LEFT . RIGHT |
+ * | EYE . EYE |
+ * | . |
+ * +----------+----------+
+ *
+ * To crop the coordinates to the left eye, divide the x
+ * coordinates by 2:
+ *
+ * / 0.5 0 0 \
+ * matrix = | 0 1 0 |
+ * \ 0 0 1 /
+ */
+ matrix_out[COL(0) + ROW(0)] = 0.5;
+ break;
+ case MULTIVIEW_STEREO_TB:
+ /*
+ * +----------+
+ * | |
+ * | LEFT |
+ * | EYE |
+ * | |
+ * +..........+
+ * | |
+ * | RIGHT |
+ * | EYE |
+ * | |
+ * +----------+
+ *
+ * To crop the coordinates to the left eye, divide the y
+ * coordinates by 2:
+ *
+ * / 1 0 0 \
+ * matrix = | 0 0.5 0 |
+ * \ 0 0 1 /
+ */
+ matrix_out[COL(1) + ROW(1)] = 0.5;
+ break;
+ default:
+ break;
+ }
+#undef COL
+#undef ROW
+}
+
static char *
BuildVertexShader(const struct vlc_gl_renderer *renderer)
{
@@ -178,11 +253,12 @@ BuildVertexShader(const struct vlc_gl_renderer *renderer)
"attribute vec2 PicCoordsIn;\n"
"varying vec2 PicCoords;\n"
"attribute vec3 VertexPosition;\n"
+ "uniform mat3 StereoMatrix;\n"
"uniform mat4 ProjectionMatrix;\n"
"uniform mat4 ZoomMatrix;\n"
"uniform mat4 ViewMatrix;\n"
"void main() {\n"
- " PicCoords = PicCoordsIn;\n"
+ " PicCoords = (StereoMatrix * vec3(PicCoordsIn, 1.0)).st;\n"
" gl_Position = ProjectionMatrix * ZoomMatrix * ViewMatrix\n"
" * vec4(VertexPosition, 1.0);\n"
"}";
@@ -245,6 +321,7 @@ opengl_link_program(struct vlc_gl_renderer *renderer)
#define GET_ALOC(x, str) GET_LOC(Attrib, renderer->aloc.x, str)
GET_ULOC(TransformMatrix, "TransformMatrix");
GET_ULOC(OrientationMatrix, "OrientationMatrix");
+ GET_ULOC(StereoMatrix, "StereoMatrix");
GET_ULOC(ProjectionMatrix, "ProjectionMatrix");
GET_ULOC(ViewMatrix, "ViewMatrix");
GET_ULOC(ZoomMatrix, "ZoomMatrix");
@@ -365,6 +442,8 @@ vlc_gl_renderer_New(vlc_gl_t *gl, const struct vlc_gl_api *api,
return NULL;
}
+ InitStereoMatrix(renderer->var.StereoMatrix, interop->fmt.multiview_mode);
+
getOrientationTransformMatrix(interop->fmt.orientation,
renderer->var.OrientationMatrix);
getViewpointMatrixes(renderer, interop->fmt.projection_mode);
@@ -829,6 +908,8 @@ static void DrawWithShaders(struct vlc_gl_renderer *renderer)
vt->UniformMatrix4fv(renderer->uloc.OrientationMatrix, 1, GL_FALSE,
renderer->var.OrientationMatrix);
+ vt->UniformMatrix3fv(renderer->uloc.StereoMatrix, 1, GL_FALSE,
+ renderer->var.StereoMatrix);
vt->UniformMatrix4fv(renderer->uloc.ProjectionMatrix, 1, GL_FALSE,
renderer->var.ProjectionMatrix);
vt->UniformMatrix4fv(renderer->uloc.ViewMatrix, 1, GL_FALSE,
@@ -839,57 +920,6 @@ static void DrawWithShaders(struct vlc_gl_renderer *renderer)
vt->DrawElements(GL_TRIANGLES, renderer->nb_indices, GL_UNSIGNED_SHORT, 0);
}
-
-static void GetTextureCropParamsForStereo(unsigned i_nbTextures,
- const float *stereoCoefs,
- const float *stereoOffsets,
- float *left, float *top,
- float *right, float *bottom)
-{
- for (unsigned i = 0; i < i_nbTextures; ++i)
- {
- float f_2eyesWidth = right[i] - left[i];
- left[i] = left[i] + f_2eyesWidth * stereoOffsets[0];
- right[i] = left[i] + f_2eyesWidth * stereoCoefs[0];
-
- float f_2eyesHeight = bottom[i] - top[i];
- top[i] = top[i] + f_2eyesHeight * stereoOffsets[1];
- bottom[i] = top[i] + f_2eyesHeight * stereoCoefs[1];
- }
-}
-
-static void TextureCropForStereo(struct vlc_gl_renderer *renderer,
- float *left, float *top,
- float *right, float *bottom)
-{
- const struct vlc_gl_interop *interop = renderer->interop;
-
- float stereoCoefs[2];
- float stereoOffsets[2];
-
- switch (renderer->fmt.multiview_mode)
- {
- case MULTIVIEW_STEREO_TB:
- // Display only the left eye.
- stereoCoefs[0] = 1; stereoCoefs[1] = 0.5;
- stereoOffsets[0] = 0; stereoOffsets[1] = 0;
- GetTextureCropParamsForStereo(interop->tex_count,
- stereoCoefs, stereoOffsets,
- left, top, right, bottom);
- break;
- case MULTIVIEW_STEREO_SBS:
- // Display only the left eye.
- stereoCoefs[0] = 0.5; stereoCoefs[1] = 1;
- stereoOffsets[0] = 0; stereoOffsets[1] = 0;
- GetTextureCropParamsForStereo(interop->tex_count,
- stereoCoefs, stereoOffsets,
- left, top, right, bottom);
- break;
- default:
- break;
- }
-}
-
int
vlc_gl_renderer_Draw(struct vlc_gl_renderer *renderer,
const video_format_t *source)
@@ -934,9 +964,6 @@ vlc_gl_renderer_Draw(struct vlc_gl_renderer *renderer,
bottom[j] = (source->i_y_offset + source->i_visible_height) * scale_h;
}
- /* TODO crop stereo using a separate transform matrix */
- TextureCropForStereo(renderer, left, top, right, bottom);
-
memset(renderer->var.TexCoordsMap, 0,
sizeof(renderer->var.TexCoordsMap));
for (unsigned j = 0; j < interop->tex_count; ++j)
diff --git a/modules/video_output/opengl/renderer.h b/modules/video_output/opengl/renderer.h
index 995fa56122..39ec2a98a0 100644
--- a/modules/video_output/opengl/renderer.h
+++ b/modules/video_output/opengl/renderer.h
@@ -63,6 +63,7 @@ struct vlc_gl_renderer
struct {
GLfloat OrientationMatrix[16];
GLfloat ProjectionMatrix[16];
+ GLfloat StereoMatrix[3*3];
GLfloat ZoomMatrix[16];
GLfloat ViewMatrix[16];
@@ -78,6 +79,7 @@ struct vlc_gl_renderer
GLint TransformMatrix;
GLint OrientationMatrix;
+ GLint StereoMatrix;
GLint ProjectionMatrix;
GLint ViewMatrix;
GLint ZoomMatrix;
--
2.25.1
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