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[core] pack extrude and line distance into unsigned byte

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instead of a signed byte. It's a bit easier to understand.

6c29251b35
This commit is contained in:
Ansis Brammanis
2016-03-28 16:58:54 -07:00
parent 196b7903d1
commit 3cc55a9dac
7 changed files with 24 additions and 16 deletions
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18
src/mbgl/geometry/line_buffer.cpp
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@@ -13,16 +13,24 @@ GLsizei LineVertexBuffer::add(vertex_type x, vertex_type y, float ex, float ey,
coords[0] = (x * 2) | tx;
coords[1] = (y * 2) | ty;
int8_t *extrude = static_cast<int8_t *>(data);
extrude[4] = ::round(extrudeScale * ex);
extrude[5] = ::round(extrudeScale * ey);
uint8_t *ubytes = static_cast<uint8_t *>(data);
// add 128 to store an byte in an unsigned byte
ubytes[4] = ::round(extrudeScale * ex) + 128;
ubytes[5] = ::round(extrudeScale * ey) + 128;
// Encode the -1/0/1 direction value into the first two bits of .z of a_data.
// Combine it with the lower 6 bits of `linesofar` (shifted by 2 bites to make
// room for the direction value). The upper 8 bits of `linesofar` are placed in
// the `w` component. `linesofar` is scaled down by `LINE_DISTANCE_SCALE` so that
// we can store longer distances while sacrificing precision.
// Encode the -1/0/1 direction value into .zw coordinates of a_data, which is normally covered
// by linesofar, so we need to merge them.
// The z component's first bit, as well as the sign bit is reserved for the direction,
// so we need to shift the linesofar.
extrude[6] = ((dir < 0) ? -1 : 1) * ((dir ? 1 : 0) | static_cast<int8_t>((linesofar << 1) & 0x7F));
extrude[7] = ((linesofar >> 6) & 0xFF) - 128;
ubytes[6] = ((dir == 0 ? 0 : (dir < 0 ? -1 : 1 )) + 1) | ((linesofar & 0x3F) << 2);
ubytes[7] = linesofar >> 6;
return idx;
}

4
src/mbgl/shader/line.vertex.glsl
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@@ -23,8 +23,8 @@ varying vec2 v_normal;
varying float v_gamma_scale;
void main() {
vec2 a_extrude = a_data.xy;
float a_direction = sign(a_data.z) * mod(a_data.z, 2.0);
vec2 a_extrude = a_data.xy - 128.0;
float a_direction = mod(a_data.z, 4.0) - 1.0;
// We store the texture normals in the most insignificant bit
// transform y so that 0 => -1 and 1 => 1

2
src/mbgl/shader/line_shader.cpp
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@@ -17,5 +17,5 @@ void LineShader::bind(GLbyte* offset) {
MBGL_CHECK_ERROR(glVertexAttribPointer(a_pos, 2, GL_SHORT, false, 8, offset + 0));
MBGL_CHECK_ERROR(glEnableVertexAttribArray(a_data));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_BYTE, false, 8, offset + 4));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_UNSIGNED_BYTE, false, 8, offset + 4));
}

6
src/mbgl/shader/linepattern.vertex.glsl
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@@ -32,9 +32,9 @@ varying float v_linesofar;
varying float v_gamma_scale;
void main() {
vec2 a_extrude = a_data.xy;
float a_direction = sign(a_data.z) * mod(a_data.z, 2.0);
float a_linesofar = (abs(floor(a_data.z / 2.0)) + (a_data.w + 128.0) * 64.0) * LINE_DISTANCE_SCALE;
vec2 a_extrude = a_data.xy - 128.0;
float a_direction = mod(a_data.z, 4.0) - 1.0;
float a_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * LINE_DISTANCE_SCALE;
// We store the texture normals in the most insignificant bit
// transform y so that 0 => -1 and 1 => 1

2
src/mbgl/shader/linepattern_shader.cpp
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@@ -17,5 +17,5 @@ void LinepatternShader::bind(GLbyte* offset) {
MBGL_CHECK_ERROR(glVertexAttribPointer(a_pos, 2, GL_SHORT, false, 8, offset + 0));
MBGL_CHECK_ERROR(glEnableVertexAttribArray(a_data));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_BYTE, false, 8, offset + 4));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_UNSIGNED_BYTE, false, 8, offset + 4));
}

6
src/mbgl/shader/linesdf.vertex.glsl
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@@ -36,9 +36,9 @@ varying vec2 v_tex_b;
varying float v_gamma_scale;
void main() {
vec2 a_extrude = a_data.xy;
float a_direction = sign(a_data.z) * mod(a_data.z, 2.0);
float a_linesofar = (abs(floor(a_data.z / 2.0)) + (a_data.w + 128.0) * 64.0) * LINE_DISTANCE_SCALE;
vec2 a_extrude = a_data.xy - 128.0;
float a_direction = mod(a_data.z, 4.0) - 1.0;
float a_linesofar = (floor(a_data.z / 4.0) + a_data.w * 64.0) * LINE_DISTANCE_SCALE;
// We store the texture normals in the most insignificant bit
// transform y so that 0 => -1 and 1 => 1

2
src/mbgl/shader/linesdf_shader.cpp
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@@ -17,5 +17,5 @@ void LineSDFShader::bind(GLbyte* offset) {
MBGL_CHECK_ERROR(glVertexAttribPointer(a_pos, 2, GL_SHORT, false, 8, offset + 0));
MBGL_CHECK_ERROR(glEnableVertexAttribArray(a_data));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_BYTE, false, 8, offset + 4));
MBGL_CHECK_ERROR(glVertexAttribPointer(a_data, 4, GL_UNSIGNED_BYTE, false, 8, offset + 4));
}