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Refactor text rendering to use less input data

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This commit is contained in:
Phireh 2024-01-06 13:16:00 +01:00
commit 678414f014
2 changed files with 57 additions and 40 deletions
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43
main.cpp
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@ -237,7 +237,7 @@ uint32_t make_gl_program(const char *pathname_vertex, const char *pathname_fragm
void render_text(const char *text, float x, float y, float scale, glm::vec3 color)
{
// TODO: Group draw calls together instead of doing 1 draw call/character. Use an atlas with GL_TEXTURE_ARRAY
// TODO: Do not make draw calls for invisible characters!
// Take tips from https://www.youtube.com/watch?v=S0PyZKX4lyI
// activate corresponding render state
glUseProgram(text_program);
@ -251,31 +251,39 @@ void render_text(const char *text, float x, float y, float scale, glm::vec3 colo
char c = *p;
charglyph_t charglyph = glyphmap[(size_t)c];
if (c == ' ') // Just advance by normal horizontal distance and prepare for next char
{
x += (charglyph.advance >> 6) * scale;
continue;
}
float xpos = x + charglyph.bearing.x * scale;
float ypos = y - (charglyph.size.y - charglyph.bearing.y) * scale;
float w = charglyph.size.x * scale;
float h = charglyph.size.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]);
// 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 }
};
// 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);
glBindBuffer(GL_ARRAY_BUFFER, 0);
//glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertices), vertices);
// render quad
glEnable(GL_CULL_FACE);
glDrawArrays(GL_TRIANGLE_FAN, 0, 4);
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)
}
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
glBindTexture(GL_TEXTURE_2D, 0);
}
@ -452,14 +460,21 @@ int main([[maybe_unused]]int argc, [[maybe_unused]]char **argv)
// text initialization
text_program = make_gl_program("shaders/text.vert", "shaders/text.frag");
static GLfloat vertex_data[] = {
0.0f, 1.0f,
0.0f, 0.0f,
1.0f, 0.0f,
1.0f, 1.0f,
};
glGenVertexArrays(1, &textvao);
glGenBuffers(1, &textvbo);
glBindVertexArray(textvao);
glBindBuffer(GL_ARRAY_BUFFER, textvbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(float) * 6 * 4, NULL, GL_DYNAMIC_DRAW);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertex_data), vertex_data, GL_STATIC_DRAW);
glEnableVertexAttribArray(0);
glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 4 * sizeof(float), 0);
glVertexAttribPointer(0, 2, GL_FLOAT, GL_FALSE, 0, 0);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);

8
shaders/text.vert
View file

@ -1,11 +1,13 @@
#version 330 core
layout (location = 0) in vec4 vertex; // <vec2 pos, vec2 tex>
layout (location = 0) in vec2 vertex; // <vec2 pos>
out vec2 texuv;
uniform mat4 transform;
uniform mat4 projection;
void main()
{
gl_Position = projection * vec4(vertex.xy, 0.0, 1.0);
texuv = vertex.zw;
gl_Position = projection * transform * vec4(vertex.xy, 0.0, 1.0);
texuv = vertex.xy;
texuv.y=1.0f-texuv.y;
}