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#include "snowflake.h"
#include "../renderer_2d.h"
#include "../mathlib.h"
#include "../list.h"
#include "../shader.h"
#include "../shaders/snowflake_vert.h"
#include "../shaders/snowflake_frag.h"
#include <cstdio>
/*
What else to do?
- Windstream that blows a certain selection of snowflakes in a loop-dee-loop pattern
- Snowflakes that land on the ground and melt
- Snowflakes that spin along the Y-axis for a three dimensional effect
*/
const Vector2 SCALE_RANGE = Vector2(16.f, 48.f);
const Vector2 VELOCITY_RANGE_X = Vector2(-10.f, 10.f);
const Vector2 VELOCITY_RANGE_Y = Vector2(-100.f, -85.f);
const Vector2 ROTATION_VELOCITY_RANGE = Vector2(-PI / 8.f, PI / 8.f);
const Vector2 WIND_VELOCITY_RANGE_X = Vector2(-3.f, 3.f);
const Vector2 WIND_VELOCITY_RANGE_Y = Vector2(3.f, 10.f);
const f32 GRAVITY = 5.f;
inline void initFlake(SnowflakeParticleRenderer* renderer, SnowflakeUpdateData* ud) {
ud->scale = randomFloatBetween(SCALE_RANGE.x, SCALE_RANGE.y);
ud->seed = randomFloatBetween(0.f, 1000.f);
// Scale velocity based on star size - larger stars fall faster
f32 sizeRatio = (ud->scale - SCALE_RANGE.x) / (SCALE_RANGE.y - SCALE_RANGE.x);
f32 velocityY = VELOCITY_RANGE_Y.x + (VELOCITY_RANGE_Y.y - VELOCITY_RANGE_Y.x) * (0.5f + sizeRatio * 0.5f);
ud->velocity = Vector2(randomFloatBetween(VELOCITY_RANGE_X.x, VELOCITY_RANGE_X.y), velocityY);
ud->position = Vector2(randomFloatBetween(0, renderer->xMax), randomFloatBetween(renderer->yMax, 4 * renderer->yMax));
ud->rotateVelocity = randomFloatBetween(ROTATION_VELOCITY_RANGE.x, ROTATION_VELOCITY_RANGE.y);
ud->rotation = 0.f;
}
void SnowflakeParticleRenderer::load(SnowflakeLoadParameters params, Renderer2d* renderer) {
numSnowflakes = params.numSnowflakes;
updateData = new SnowflakeUpdateData[params.numSnowflakes];
xMax = static_cast<f32>(renderer->context->width);
yMax = static_cast<f32>(renderer->context->height);
// Initialize each snowflake
for (i32 s = 0; s < numSnowflakes; s++) {
auto ud = &updateData[s];
initFlake(this, ud);
}
// Load custom snowflake shader
shader = loadShader(shader_snowflake_vert, shader_snowflake_frag);
useShader(shader);
// Get attribute and uniform locations
attributes.position = getShaderAttribute(shader, "position");
attributes.instancePos = getShaderAttribute(shader, "instancePos");
attributes.instanceRot = getShaderAttribute(shader, "instanceRot");
attributes.instanceScale = getShaderAttribute(shader, "instanceScale");
attributes.instanceSeed = getShaderAttribute(shader, "instanceSeed");
uniforms.projection = getShaderUniform(shader, "projection");
uniforms.model = getShaderUniform(shader, "model");
// Create base quad geometry (just a square from -1 to 1)
Vector2 quadVertices[] = {
Vector2(-1.0f, -1.0f),
Vector2( 1.0f, -1.0f),
Vector2( 1.0f, 1.0f),
Vector2(-1.0f, -1.0f),
Vector2( 1.0f, 1.0f),
Vector2(-1.0f, 1.0f)
};
// Setup VAO
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// Create and setup quad VBO (static geometry)
glGenBuffers(1, &quadVbo);
glBindBuffer(GL_ARRAY_BUFFER, quadVbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(quadVertices), quadVertices, GL_STATIC_DRAW);
glEnableVertexAttribArray(attributes.position);
glVertexAttribPointer(attributes.position, 2, GL_FLOAT, GL_FALSE, sizeof(Vector2), (GLvoid*)0);
// Create instance VBO (dynamic data)
glGenBuffers(1, &instanceVbo);
glBindBuffer(GL_ARRAY_BUFFER, instanceVbo);
glBufferData(GL_ARRAY_BUFFER, numSnowflakes * sizeof(SnowflakeInstanceData), NULL, GL_DYNAMIC_DRAW);
// Setup instance attributes
glEnableVertexAttribArray(attributes.instancePos);
glVertexAttribPointer(attributes.instancePos, 2, GL_FLOAT, GL_FALSE, sizeof(SnowflakeInstanceData), (GLvoid*)offsetof(SnowflakeInstanceData, position));
glVertexAttribDivisor(attributes.instancePos, 1);
glEnableVertexAttribArray(attributes.instanceRot);
glVertexAttribPointer(attributes.instanceRot, 1, GL_FLOAT, GL_FALSE, sizeof(SnowflakeInstanceData), (GLvoid*)offsetof(SnowflakeInstanceData, rotation));
glVertexAttribDivisor(attributes.instanceRot, 1);
glEnableVertexAttribArray(attributes.instanceScale);
glVertexAttribPointer(attributes.instanceScale, 1, GL_FLOAT, GL_FALSE, sizeof(SnowflakeInstanceData), (GLvoid*)offsetof(SnowflakeInstanceData, scale));
glVertexAttribDivisor(attributes.instanceScale, 1);
glEnableVertexAttribArray(attributes.instanceSeed);
glVertexAttribPointer(attributes.instanceSeed, 1, GL_FLOAT, GL_FALSE, sizeof(SnowflakeInstanceData), (GLvoid*)offsetof(SnowflakeInstanceData, seed));
glVertexAttribDivisor(attributes.instanceSeed, 1);
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
inline void resetFlake(SnowflakeParticleRenderer* renderer, SnowflakeUpdateData* ud) {
ud->position.y = 2 * renderer->yMax;
// Scale velocity based on star size - larger stars fall faster
f32 sizeRatio = (ud->scale - SCALE_RANGE.x) / (SCALE_RANGE.y - SCALE_RANGE.x);
f32 velocityY = VELOCITY_RANGE_Y.x + (VELOCITY_RANGE_Y.y - VELOCITY_RANGE_Y.x) * (0.5f + sizeRatio * 0.5f);
ud->velocity = Vector2(randomFloatBetween(VELOCITY_RANGE_X.x, VELOCITY_RANGE_X.y), velocityY);
ud->rotation = 0;
}
inline void updateFlake(SnowflakeParticleRenderer* renderer, SnowflakeUpdateData* ud, i32 s, f32 dtSeconds) {
ud->velocity = ud->velocity + Vector2(0, -(GRAVITY * dtSeconds));
//if (addWind) ud->velocity += renderer->windSpeed;
ud->position += ud->velocity * dtSeconds;
ud->rotation += ud->rotateVelocity * dtSeconds;
if (ud->position.y <= -ud->scale) {
resetFlake(renderer, ud);
}
}
void SnowflakeParticleRenderer::update(f32 dtSeconds) {
timeUntilNextWindSeconds -= dtSeconds;
if (timeUntilNextWindSeconds < 0) {
timeUntilNextWindSeconds = randomFloatBetween(2.5f, 10.f);
}
for (i32 s = 0; s < numSnowflakes; s++) {
SnowflakeUpdateData* ud = &updateData[s];
updateFlake(this, ud, s, dtSeconds);
}
}
void SnowflakeParticleRenderer::render(Renderer2d* renderer) {
useShader(shader);
setShaderMat4(uniforms.projection, renderer->projection);
setShaderMat4(uniforms.model, model);
// Prepare instance data
SnowflakeInstanceData* instanceData = new SnowflakeInstanceData[numSnowflakes];
for (i32 s = 0; s < numSnowflakes; s++) {
instanceData[s].position = updateData[s].position;
instanceData[s].rotation = updateData[s].rotation;
instanceData[s].scale = updateData[s].scale;
instanceData[s].seed = updateData[s].seed;
}
// Upload instance data
glBindBuffer(GL_ARRAY_BUFFER, instanceVbo);
glBufferSubData(GL_ARRAY_BUFFER, 0, numSnowflakes * sizeof(SnowflakeInstanceData), instanceData);
// Draw instanced
glBindVertexArray(vao);
glDrawArraysInstanced(GL_TRIANGLES, 0, 6, numSnowflakes);
glBindVertexArray(0);
delete[] instanceData;
}
void SnowflakeParticleRenderer::unload() {
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &quadVbo);
glDeleteBuffers(1, &instanceVbo);
glDeleteProgram(shader);
vao = 0;
quadVbo = 0;
instanceVbo = 0;
shader = 0;
delete[] updateData;
}
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