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GLES2: Get sin/cos out of vertex shader 

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 M?ller <schnitzeltony@gmail.com>
This commit is contained in:
Andreas M?ller 2018-08-28 12:57:51 -07:00
parent 044b00dcae
commit 87bc1fb552
2 changed files with 21 additions and 10 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

17
src/render/opengles2/SDL_render_gles2.c
View File

@ -1534,7 +1534,7 @@ 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]);
@ -1549,7 +1549,7 @@ 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;
@ -1857,6 +1857,8 @@ 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)
@ -1865,8 +1867,9 @@ 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);
@ -1876,7 +1879,11 @@ 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);
@ -1905,7 +1912,7 @@ 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));

14
src/render/opengles2/SDL_shaders_gles2.c
View File

@ -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; \