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#include "Snowflake.h"
#include "Renderer2d.h"
#include "mathlib.h"
#include "List.h"
const Vector4 snowColor = Vector4(1.0, 0.98, 0.98, 1);
inline void generateSnowflakeShape(List<Renderer2dVertex>* vertices, int32 numArms, float32 radius) {
float32 dx = ((2 * PI) / numArms) / 3.0;
for (int32 centerIdx = 0; centerIdx < (3 * numArms); centerIdx+=3) {
float32 degreeStart = dx * centerIdx;
float32 degreeEnd = dx * (centerIdx + 1);
float32 cosStart = cosf(degreeStart);
float32 cosEnd = cosf(degreeEnd);
float32 sinStart = sinf(degreeStart);
float32 sinEnd = sinf(degreeEnd);
Vector2 leftEnd = Vector2(radius * cosStart, radius * sinStart);
Vector2 rightEnd = Vector2(radius * cosEnd, radius * sinEnd);
Vector2 diff = (rightEnd - leftEnd) / 2.0;
Vector2 leftStart = Vector2(-diff.x, -diff.y);
Vector2 rightStart = diff;
vertices->add({ leftStart, snowColor, Mat4x4() });
vertices->add({ leftEnd, snowColor, Mat4x4() });
vertices->add({ rightEnd, snowColor, Mat4x4() });
vertices->add({ rightEnd, snowColor, Mat4x4() });
vertices->add({ rightStart, snowColor, Mat4x4() });
vertices->add({ leftStart, snowColor, Mat4x4() });
}
}
inline void initFlake(SnowflakeParticleRenderer* renderer, SnowflakeUpdateData* ud) {
ud->vtxIdx = renderer->vertices.numElements;
generateSnowflakeShape(&renderer->vertices, 6, randomFloatBetween(8.f, 24.f);
ud->numVertices = renderer->vertices.numElements - ud->vtxIdx;
}
inline void spawnFlake(SnowflakeParticleRenderer* renderer, SnowflakeUpdateData* ud) {
ud->velocity = Vector2(randomFloatBetween(-10, 10), randomFloatBetween(-100, -85));
ud->position = Vector2(randomFloatBetween(0, renderer->xMax), randomFloatBetween(renderer->yMax, renderer->yMax + 256));
}
inline void findAndSpawnNextFlake(SnowflakeParticleRenderer* renderer) {
do {
renderer->endIndex++;
if (renderer->endIndex >= renderer->numSnowflakes)
renderer->endIndex = 0;
} while (renderer->updateData[renderer->endIndex].onGround);
spawnFlake(renderer, &renderer->updateData[renderer->endIndex]);
}
void SnowflakeParticleRenderer::load(SnowflakeLoadParameters params, Renderer2d* renderer) {
startIndex = 0;
spawnIntervalSeconds = params.spawnIntervalSeconds;
endIndex = params.initialSnowflakeCount;
numSnowflakes = params.maxSnowflakes;
updateData = new SnowflakeUpdateData[params.maxSnowflakes];
xMax = static_cast<float32>(renderer->context->width);
yMax = static_cast<float32>(renderer->context->height);
// Initialize each snow flake with its shape
for (int32 s = 0; s < numSnowflakes; s++) {
auto ud = &updateData[s];
initFlake(this, ud);
if (s < endIndex) {
spawnFlake(this, ud);
}
}
useShader(renderer->shader);
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
glGenBuffers(1, &vbo);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, vertices.numElements * sizeof(Renderer2dVertex), &vertices.data[0], GL_DYNAMIC_DRAW);
glEnableVertexAttribArray(renderer->attributes.position);
glVertexAttribPointer(renderer->attributes.position, 2, GL_FLOAT, GL_FALSE, sizeof(Renderer2dVertex), (GLvoid *)0);
glEnableVertexAttribArray(renderer->attributes.color);
glVertexAttribPointer(renderer->attributes.color, 4, GL_FLOAT, GL_FALSE, sizeof(Renderer2dVertex), (GLvoid *)offsetof(Renderer2dVertex, color));
for (int32 idx = 0; idx < 4; idx++) {
int32 offset = (4 * sizeof(float32)) * idx;
glEnableVertexAttribArray(renderer->attributes.vMatrix + idx);
glVertexAttribPointer(renderer->attributes.vMatrix + idx,
4,
GL_FLOAT,
GL_FALSE,
sizeof(Renderer2dVertex),
(GLvoid *)(offsetof(Renderer2dVertex, vMatrix) + offset));
//glVertexAttribDivisor(renderer->attributes.vMatrix + idx, 1);
}
glBindBuffer(GL_ARRAY_BUFFER, 0);
glBindVertexArray(0);
}
void SnowflakeParticleRenderer::update(float32 dtSeconds) {
timeUntilNextSpawnSeconds -= dtSeconds;
if (timeUntilNextSpawnSeconds < 0) {
timeUntilNextSpawnSeconds = spawnIntervalSeconds;
findAndSpawnNextFlake(this);
}
for (int32 s = startIndex; s < endIndex; s++) {
SnowflakeUpdateData* ud = &updateData[s];
ud->position += ud->velocity * dtSeconds;
Mat4x4 m = Mat4x4().translateByVec2(ud->position);
for (int32 v = ud->vtxIdx; v < (ud->vtxIdx + ud->numVertices); v++) {
vertices.data[v].vMatrix = m;
}
}
}
void SnowflakeParticleRenderer::render(Renderer2d* renderer) {
auto startVertex = &updateData[startIndex];
auto endVertex = &updateData[endIndex];
int32 numVertices = (endVertex->vtxIdx + endVertex->numVertices) - startVertex->vtxIdx;
setShaderMat4(renderer->uniforms.model, model);
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferSubData(GL_ARRAY_BUFFER, 0, numVertices * sizeof(Renderer2dVertex), &vertices.data[startVertex->vtxIdx]);
glBindVertexArray(vao);
glDrawArrays(GL_TRIANGLES, 0, numVertices);
glBindVertexArray(0);
}
void SnowflakeParticleRenderer::unload() {
glDeleteVertexArrays(1, &vao);
glDeleteBuffers(1, &vbo);
vertices.deallocate();
delete [] updateData;
}
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