It is better to load the texture with the atlas of the whole GUI once. And use her.
In order to draw a texture from the atlas, we need to slightly modify the standard shader (drawimage), and save it under a different name (drawimagerect).
Shader
#version 400 uniform vec4 drawcolor; uniform sampler2D texture0; uniform vec4 rect; in vec2 vTexCoords0; out vec4 fragData0; void main(void) { ivec2 ts = textureSize(texture0, 0); vec4 coord = vec4(rect.x / ts.x, rect.y / ts.y, rect.z / ts.x, rect.w / ts.y); vec2 uv = coord.xy + (vTexCoords0 * coord.zw); fragData0 = drawcolor * texture(texture0,uv); } Now we can draw a texture from the atlas:
void drawImageRect(Texture* texture, float x, float y, Vec4 rect) { Context* context = Context::GetCurrent(); context->SetShader(Shader::Load("Shaders/Drawing/drawimagerect.shader")); context->GetShader()->SetVec4("rect", rect); context->DrawImage(texture, x, y, rect.z, rect.w); context->SetShader(NULL); } void drawImageRect(Texture* texture, float x, float y, float width, float height, Vec4 rect) { Context* context = Context::GetCurrent(); context->SetShader(Shader::Load("Shaders/Drawing/drawimagerect.shader")); context->GetShader()->SetVec4("rect", rect); context->DrawImage(texture, x, y, width, height); context->SetShader(NULL); } Animation
To play the animation we need to get the coordinates of all the frames in the atlas. Naturally, we won't do this manually, will write a small algorithm.
bool isEmptyFrame(char* pixels, int textureWidth, iVec2 position, iVec2 frameSize, const bool alpha=true, const iVec3 colorBg=iVec3()) { unsigned char r, g, b, a; int level = 0; for (int y = position.y; y < position.y + frameSize.y; y++) { for (int x = position.x; x < position.x + frameSize.x; x++) { int p = (y * textureWidth + x) * 4; memcpy(&r, pixels + p + 0, 1); memcpy(&g, pixels + p + 1, 1); memcpy(&b, pixels + p + 2, 1); memcpy(&a, pixels + p + 3, 1); if (!alpha) { if ((int)r == colorBg.r && (int)g == colorBg.g && (int)b == colorBg.b) { level++; } else { return false; } } else { if ((int)a == 0) { level++; } else { return false; } } } } float percent = (float)((float)level / (float)(frameSize.x * frameSize.y)) * 100.0f; if (percent >= 100.0f) { return true; } return false; } void getFrames(Texture* texture, iVec2 framesize, std::vector<Vec4> &frames) { if (texture == nullptr) return; int horizontLine = texture->GetWidth() / framesize.x; int verticalLine = texture->GetHeight() / framesize.y; int frameCount = horizontLine * verticalLine; int currentHorizont = 0; int currentVertical = 0; iVec2 framePosition = iVec2(); iVec2 frameSize = framesize; char* pixels = (char*)malloc(texture->GetMipmapSize(0) * 8); texture->GetPixels(pixels); System::Print((std::string)"Get frames from texture atlas \"" + texture->GetPath() + "\"..."); // Push first frame int skipCount = 0; if (!isEmptyFrame(pixels, texture->GetWidth(), framePosition, frameSize)) { frames.push_back(Vec4((float)framePosition.x, (float)framePosition.y, (float)frameSize.x, (float)frameSize.y)); } else { skipCount++; System::Print((std::string)"Frame #0" + " is empty. (skip)"); } for (int i = 1; i < frameCount; i++) { if (currentHorizont < horizontLine - 1) { currentHorizont++; framePosition.x = frameSize.x * currentHorizont; } else { if (currentVertical < verticalLine - 1) { currentVertical++; framePosition.x = 0; framePosition.y = frameSize.y * currentVertical; currentHorizont = 0; } } if (!isEmptyFrame(pixels, texture->GetWidth(), framePosition, frameSize)) { frames.push_back(Vec4((float)framePosition.x, (float)framePosition.y, (float)frameSize.x, (float)frameSize.y)); } else { skipCount++; System::Print((std::string)"Frame #" + std::to_string(i) + " is empty. (skip)"); } } System::Print((std::string)"Frame count: " + std::to_string(frames.size()) + ", skip: " + std::to_string(skipCount)); free(pixels); } Now that we have all the frames, we can play the animation.
Texture* atlas = Texture::Load("Textures/atlas.tex"); std::vector<Vec4> frames; getFrames(atlas, iVec2(96, 96), frames); float frame = 0.0f; float frameend = frames.size(); float framebegin = 0.0f; float speed = 0.1f; //Loop frame += Time::GetSpeed() * speed; frame = fmodf(frame, frameend - framebegin) + framebegin; //Draw drawImageRect(atlas, 25.0f, 25.0f, frames[(int)frame]); Updates: [04.04.2020] [+] Added check for empty frames.
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