Fix canvas particle material for old GLSL versions

1 files changed, 8 insertions, 12 deletions

diff --git a/scene/2d/canvas_item.cpp b/scene/2d/canvas_item.cpp
index 41cee7335e..2739f71543 100644
--- a/scene/2d/canvas_item.cpp
+++ b/scene/2d/canvas_item.cpp
@@ -131,19 +131,15 @@ void CanvasItemMaterial::_update_shader() {
 
 		code += "\tVERTEX.xy /= vec2(h_frames, v_frames);\n";
 
-		code += "\tint total_frames = particles_anim_h_frames * particles_anim_v_frames;\n";
-		code += "\tint frame = int(float(total_frames) * INSTANCE_CUSTOM.z);\n";
-		code += "\tif (particles_anim_loop) {\n";
-		code += "\t\tframe = int(abs(frame) % total_frames);\n";
+		code += "\tfloat particle_total_frames = float(particles_anim_h_frames * particles_anim_v_frames);\n";
+		code += "\tfloat particle_frame = floor(INSTANCE_CUSTOM.z * float(particle_total_frames));\n";
+		code += "\tif (!particles_anim_loop) {\n";
+		code += "\t\tparticle_frame = clamp(particle_frame, 0.0, particle_total_frames - 1.0);\n";
 		code += "\t} else {\n";
-		code += "\t\tframe = clamp(frame, 0, total_frames - 1);\n";
-		code += "\t}\n";
-
-		code += "\tfloat frame_w = 1.0 / h_frames;\n";
-		code += "\tfloat frame_h = 1.0 / v_frames;\n";
-		code += "\tUV.x = UV.x * frame_w + frame_w * float(frame % particles_anim_h_frames);\n";
-		code += "\tUV.y = UV.y * frame_h + frame_h * float(frame / particles_anim_h_frames);\n";
-
+		code += "\t\tparticle_frame = mod(particle_frame, particle_total_frames);\n";
+		code += "\t}";
+		code += "\tUV /= vec2(h_frames, v_frames);\n";
+		code += "\tUV += vec2(mod(particle_frame, h_frames) / h_frames, floor(particle_frame / h_frames) / v_frames);\n";
 		code += "}\n";
 	}