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[patch] [PATCH] GLES2: Get sin/cos out of vertex shader

0001-GLES2-Get-sin-cos-out-of-vertex-shader.patch (text/plain), 6.16 KB, created by Andreas Müller on 2018-08-26 14:10:30 UTC

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Creator: Andreas Müller

Created: 2018-08-26 14:10:30 UTC

Size: 6.16 KB

patch

obsolete

>From c215ba1d52a3d4ef03af3ab1a5baa1863f812aed Mon Sep 17 00:00:00 2001
>From: =?UTF-8?q?Andreas=20M=C3=BCller?= <schnitzeltony@gmail.com>
>Date: Fri, 24 Aug 2018 23:10:25 +0200
>Subject: [PATCH] GLES2: Get sin/cos out of vertex shader
>MIME-Version: 1.0
>Content-Type: text/plain; charset=UTF-8
>Content-Transfer-Encoding: 8bit
>
>The only place angle is activated and causes effect is RenderCopyEx. All other
>methods which use vertex shader, leave angle disabled and cause useless sin/cos
>calculation in shader.
>
>To get around shader's interface is changed to a vector that contains results
>of sin and cos. To behave properly when disabled, cos value is set with offset
>-1.0 making 0.0 default when deactivated.
>
>As nice side effect it simplifies GLES2_UpdateVertexBuffer: All attributes are
>vectors now.
>
>Additional background:
>
>* On RaspberryPi it gives a performace win for operations. Tested with
>  [1] numbers go down for 5-10% (not easy to estimate due to huge variation).
>* SDL_RenderCopyEx was tested with [2]
>* It works around left rotated display caused by low accuracy sin implemetation
>  in RaspberryPi/VC4 [3]
>
>[1] https://github.com/schnitzeltony/sdl2box
>[2] https://github.com/schnitzeltony/sdl2rendercopyex
>[3] https://github.com/anholt/mesa/issues/110
>
>Signed-off-by: Andreas MÃ¼ller <schnitzeltony@gmail.com>
>---
> src/render/opengles2/SDL_render_gles2.c  | 17 ++++++++++++-----
> src/render/opengles2/SDL_shaders_gles2.c | 14 +++++++++-----
> 2 files changed, 21 insertions(+), 10 deletions(-)
>
>diff --git a/src/render/opengles2/SDL_render_gles2.c b/src/render/opengles2/SDL_render_gles2.c
>index 14671f7c8..7c54a7333 100644
>--- a/src/render/opengles2/SDL_render_gles2.c
>+++ b/src/render/opengles2/SDL_render_gles2.c
>@@ -1530,7 +1530,7 @@ GLES2_UpdateVertexBuffer(SDL_Renderer *renderer, GLES2_Attribute attr,
>     GLES2_DriverContext *data = (GLES2_DriverContext *)renderer->driverdata;
> 
> #if !SDL_GLES2_USE_VBOS
>-    data->glVertexAttribPointer(attr, attr == GLES2_ATTRIBUTE_ANGLE ? 1 : 2, GL_FLOAT, GL_FALSE, 0, vertexData);
>+    data->glVertexAttribPointer(attr, 2, GL_FLOAT, GL_FALSE, 0, vertexData);
> #else
>     if (!data->vertex_buffers[attr]) {
>         data->glGenBuffers(1, &data->vertex_buffers[attr]);
>@@ -1545,7 +1545,7 @@ GLES2_UpdateVertexBuffer(SDL_Renderer *renderer, GLES2_Attribute attr,
>         data->glBufferSubData(GL_ARRAY_BUFFER, 0, dataSizeInBytes, vertexData);
>     }
> 
>-    data->glVertexAttribPointer(attr, attr == GLES2_ATTRIBUTE_ANGLE ? 1 : 2, GL_FLOAT, GL_FALSE, 0, 0);
>+    data->glVertexAttribPointer(attr, 2, GL_FLOAT, GL_FALSE, 0, 0);
> #endif
> 
>     return 0;
>@@ -1853,6 +1853,8 @@ GLES2_RenderCopy(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rect *s
>     return GL_CheckError("", renderer);
> }
> 
>+#define PI 3.14159265f
>+
> static int
> GLES2_RenderCopyEx(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rect *srcrect,
>                  const SDL_FRect *dstrect, const double angle, const SDL_FPoint *center, const SDL_RendererFlip flip)
>@@ -1861,8 +1863,9 @@ GLES2_RenderCopyEx(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rect
>     GLfloat vertices[8];
>     GLfloat texCoords[8];
>     GLfloat translate[8];
>-    GLfloat fAngle[4];
>+    GLfloat fAngle[8];
>     GLfloat tmp;
>+    float radian_angle;
> 
>     GLES2_ActivateRenderer(renderer);
> 
>@@ -1872,7 +1875,11 @@ GLES2_RenderCopyEx(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rect
> 
>     data->glEnableVertexAttribArray(GLES2_ATTRIBUTE_CENTER);
>     data->glEnableVertexAttribArray(GLES2_ATTRIBUTE_ANGLE);
>-    fAngle[0] = fAngle[1] = fAngle[2] = fAngle[3] = (GLfloat)(360.0f - angle);
>+
>+    radian_angle = PI * (360.0f - angle) / 180.f;
>+    fAngle[0] = fAngle[2] = fAngle[4] = fAngle[6] = (GLfloat)sin(radian_angle);
>+    /* render expects cos value - 1 (see GLES2_VertexSrc_Default_) */
>+    fAngle[1] = fAngle[3] = fAngle[5] = fAngle[7] = (GLfloat)cos(radian_angle) - 1.0f;
>     /* Calculate the center of rotation */
>     translate[0] = translate[2] = translate[4] = translate[6] = (center->x + dstrect->x);
>     translate[1] = translate[3] = translate[5] = translate[7] = (center->y + dstrect->y);
>@@ -1901,7 +1908,7 @@ GLES2_RenderCopyEx(SDL_Renderer *renderer, SDL_Texture *texture, const SDL_Rect
>     data->glVertexAttribPointer(GLES2_ATTRIBUTE_CENTER, 2, GL_FLOAT, GL_FALSE, 0, translate);
>     data->glVertexAttribPointer(GLES2_ATTRIBUTE_POSITION, 2, GL_FLOAT, GL_FALSE, 0, vertices);*/
> 
>-    GLES2_UpdateVertexBuffer(renderer, GLES2_ATTRIBUTE_ANGLE, fAngle, 4 * sizeof(GLfloat));
>+    GLES2_UpdateVertexBuffer(renderer, GLES2_ATTRIBUTE_ANGLE, fAngle, 8 * sizeof(GLfloat));
>     GLES2_UpdateVertexBuffer(renderer, GLES2_ATTRIBUTE_CENTER, translate, 8 * sizeof(GLfloat));
>     GLES2_UpdateVertexBuffer(renderer, GLES2_ATTRIBUTE_POSITION, vertices, 8 * sizeof(GLfloat));
> 
>diff --git a/src/render/opengles2/SDL_shaders_gles2.c b/src/render/opengles2/SDL_shaders_gles2.c
>index b0bcdff25..f428a4945 100644
>--- a/src/render/opengles2/SDL_shaders_gles2.c
>+++ b/src/render/opengles2/SDL_shaders_gles2.c
>@@ -30,20 +30,24 @@
> /*************************************************************************************************
>  * Vertex/fragment shader source                                                                 *
>  *************************************************************************************************/
>-
>+/* Notes on a_angle:
>+   * It is a vector containing sin and cos for rotation matrix
>+   * To get correct rotation for most cases when a_angle is disabled cos
>+     value is decremented by 1.0 to get proper output with 0.0 which is
>+     default value
>+*/
> static const Uint8 GLES2_VertexSrc_Default_[] = " \
>     uniform mat4 u_projection; \
>     attribute vec2 a_position; \
>     attribute vec2 a_texCoord; \
>-    attribute float a_angle; \
>+    attribute vec2 a_angle; \
>     attribute vec2 a_center; \
>     varying vec2 v_texCoord; \
>     \
>     void main() \
>     { \
>-        float angle = radians(a_angle); \
>-        float c = cos(angle); \
>-        float s = sin(angle); \
>+        float s = a_angle[0]; \
>+        float c = a_angle[1] + 1.0; \
>         mat2 rotationMatrix = mat2(c, -s, s, c); \
>         vec2 position = rotationMatrix * (a_position - a_center) + a_center; \
>         v_texCoord = a_texCoord; \
>-- 
>2.14.4
>

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We are currently migrating Bugzilla to GitHub issues.Any changes made to the bug tracker now will be lost, so please do not post new bugs or make changes to them.When we're done, all bug URLs will redirect to their equivalent location on the new bug tracker.

We are currently migrating Bugzilla to GitHub issues.
Any changes made to the bug tracker now will be lost, so please do not post new bugs or make changes to them.
When we're done, all bug URLs will redirect to their equivalent location on the new bug tracker.