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Optimize text rendering for long strings

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This commit is contained in:
Phireh 2024-01-06 14:35:11 +01:00
commit 3b78739efd
3 changed files with 71 additions and 56 deletions
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95
main.cpp
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@ -76,7 +76,7 @@ struct debug_clock_t
#define TIME_BLOCK(name) debug_clock_t _name_##timer(#name, __COUNTER__);
struct charglyph_t {
uint32_t tex; // handle to glyph texture
int32_t tex; // index of character in tex array
glm::ivec2 size; // 2d dimensions
glm::ivec2 bearing; // offset from baseline to left/top of glyph
uint32_t advance; // offset to next glyph
@ -109,10 +109,16 @@ struct selection_t {
int32_t nselected;
};
const int32_t ARRAY_LIMIT = 400;
charglyph_t glyphmap[128];
uint32_t text_program;
uint32_t textvao, textvbo;
uint32_t hex_program;
uint32_t texture_array;
glm::mat4 transforms[ARRAY_LIMIT];
int32_t letter_map[ARRAY_LIMIT];
// error processing
enum err_type {
@ -238,16 +244,24 @@ void render_text(const char *text, float x, float y, float scale, glm::vec3 colo
{
// TODO: Group draw calls together instead of doing 1 draw call/character. Use an atlas with GL_TEXTURE_ARRAY
// Take tips from https://www.youtube.com/watch?v=S0PyZKX4lyI
scale *= 48.0f/256;
// activate corresponding render state
glUseProgram(text_program);
glUniform3f(glGetUniformLocation(text_program, "text_color"), color.x, color.y, color.z);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
glBindVertexArray(textvao);
glBindBuffer(GL_ARRAY_BUFFER, textvbo);
int idx = 0;
// iterate through 128 ASCI characters
for (const char *p = text; *p != '\0'; ++p)
{
// Avoid drawing more than 400 chars at a time
if (idx == ARRAY_LIMIT - 1)
break;
char c = *p;
charglyph_t charglyph = glyphmap[(size_t)c];
@ -258,31 +272,19 @@ void render_text(const char *text, float x, float y, float scale, glm::vec3 colo
}
float xpos = x + charglyph.bearing.x * scale;
float ypos = y - (charglyph.size.y - charglyph.bearing.y) * scale;
float ypos = y - (256 - charglyph.bearing.y) * scale;
glm::mat4 transform = glm::translate(glm::mat4(1.0f), glm::vec3(xpos, ypos, 0)) * glm::scale(glm::mat4(1.0f), glm::vec3(charglyph.size.x * scale, charglyph.size.y * scale, 0));
glUniformMatrix4fv(glGetUniformLocation(text_program, "transform"), 1, GL_FALSE, &transform[0][0]);
transforms[idx] = glm::translate(glm::mat4(1.0f), glm::vec3(xpos, ypos, 0)) * glm::scale(glm::mat4(1.0f), glm::vec3(256 * scale, 256 * scale, 0));
letter_map[idx] = charglyph.tex;
// update VBO for each character
// float vertices[4][4] = {
// { xpos, ypos + h, 0.0f, 0.0f },
// { xpos, ypos, 0.0f, 1.0f },
// { xpos + w, ypos, 1.0f, 1.0f },
// { xpos + w, ypos + h, 1.0f, 0.0f }
// };
// render glyph texture over quad
glBindTexture(GL_TEXTURE_2D, charglyph.tex);
// update content of VBO memory
glBindBuffer(GL_ARRAY_BUFFER, textvbo);
//glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
// render quad
glEnable(GL_CULL_FACE);
glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, 1);
glDisable(GL_CULL_FACE);
// now advance cursors for next glyph (note that advance is number of 1/64 pixels)
x += (charglyph.advance >> 6) * scale; // bitshift by 6 to get value in pixels (2^6 = 64)
++idx;
}
glUniformMatrix4fv(glGetUniformLocation(text_program, "transforms"), idx, GL_FALSE, &transforms[0][0][0]);
glUniform1iv(glGetUniformLocation(text_program, "letter_map"), idx, &letter_map[0]);
glDrawArraysInstanced(GL_TRIANGLE_FAN, 0, 4, idx);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
@ -413,10 +415,15 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
MAIN_ERROR(ERR_FONT_INIT);
}
FT_Set_Pixel_Sizes(face, 0, 48);
FT_Set_Pixel_Sizes(face, 256, 256);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1); // disable byte-alignment restriction
glGenTextures(1, &texture_array);
glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D_ARRAY, texture_array);
glTexImage3D(GL_TEXTURE_2D_ARRAY, 0, GL_R8, 256, 256, 128, 0, GL_RED, GL_UNSIGNED_BYTE, 0);
for (unsigned char c = 0; c < 128; c++)
{
// load character glyph
@ -424,32 +431,24 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
{
MAIN_ERROR(ERR_CHAR_LOAD);
}
// generate texture
uint32_t texture;
glGenTextures(1, &texture);
glBindTexture(GL_TEXTURE_2D, texture);
glTexImage2D(
GL_TEXTURE_2D,
0,
GL_RED,
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
0,
GL_RED,
GL_UNSIGNED_BYTE,
face->glyph->bitmap.buffer
);
glTexSubImage3D(GL_TEXTURE_2D_ARRAY,0, 0, 0, int(c),
face->glyph->bitmap.width,
face->glyph->bitmap.rows,
1, GL_RED, GL_UNSIGNED_BYTE,
face->glyph->bitmap.buffer);
// set texture options
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D_ARRAY, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
// now store character for later use
charglyph_t charglyph = {
texture,
glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
(uint32_t)face->glyph->advance.x
int(c),
glm::ivec2(face->glyph->bitmap.width, face->glyph->bitmap.rows),
glm::ivec2(face->glyph->bitmap_left, face->glyph->bitmap_top),
(uint32_t)face->glyph->advance.x
};
glyphmap[c] = charglyph;
}
@ -460,6 +459,12 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
// text initialization
text_program = make_gl_program("shaders/text.vert", "shaders/text.frag");
for (int i = 0; i < ARRAY_LIMIT; ++i)
{
letter_map[i] = 0;
transforms[i] = glm::mat4(1.0f);
}
static GLfloat vertex_data[] = {
0.0f, 1.0f,
0.0f, 0.0f,

12
shaders/text.frag
View file

@ -1,12 +1,18 @@
#version 330 core
in vec2 texuv;
out vec4 color;
uniform sampler2D text;
in VS_OUT {
vec2 texuv;
flat int index;
} fs_in;
uniform sampler2DArray text;
uniform int letter_map[400];
uniform vec3 text_color;
void main()
{
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, texuv).r);
vec4 sampled = vec4(1.0, 1.0, 1.0, texture(text, vec3(fs_in.texuv.xy, letter_map[fs_in.index])).r);
color = vec4(text_color, 1.0) * sampled;
}

14
shaders/text.vert
View file

@ -1,13 +1,17 @@
#version 330 core
layout (location = 0) in vec2 vertex; // <vec2 pos>
out vec2 texuv;
uniform mat4 transform;
out VS_OUT {
vec2 texuv;
flat int index;
} vs_out;
uniform mat4 transforms[400];
uniform mat4 projection;
void main()
{
gl_Position = projection * transform * vec4(vertex.xy, 0.0, 1.0);
texuv = vertex.xy;
texuv.y=1.0f-texuv.y;
gl_Position = projection * transforms[gl_InstanceID] * vec4(vertex.xy, 0.0, 1.0);
vs_out.index = gl_InstanceID;
vs_out.texuv = vec2(vertex.x, 1.0f - vertex.y);
}