Fire Joker

Every drawing app 📱 that mentions perspective either traces over your photo 📸 or plays you a video 🎬 about vanishing points. Fire Joker does neither. It is a measuring instrument: you photograph a real scene, mark the edges you can actually see 👀 in it, and the app 📱 solves that camera 📷's own geometry — its vanishing points, its horizon, its focal length — and hands the grid back to you to draw against.

The heart of Fire Joker is the VP Solver Rail. Photograph a room corner, a street or a box on your desk, straighten the shot, then drag ✋ "edge rakers" onto the converging edges in the picture. Two rakers meet at an exact intersection; from three up, the vanishing point is fitted by least squares and a live convergence error ❌ reads out in degrees, colour-coded, with the worst-offending raker highlighted so you know 💡 which one is fighting the others. Under half a degree is a tight solve. Work a second axis group and the app 📱 reports whether you are looking at one-, two- or three-point perspective, and derives the principal point, the focal length, the horizontal and vertical field of view, and the correct viewing distance for the finished drawing. When two edge groups turn out not to be perpendicular in the real world, it says so plainly rather than inventing a number 🔢.

That solved grid is then reusable. Fade the photograph out to draw on bare geometry, set how many convergence rays each vanishing point throws, toggle floor, ceiling and wall planes, and pull guide lines that lock themselves to whichever vanishing point they point at. Four calculators run off the same numbers 🔢: measuring points, which lay off true real-world lengths along a receding edge; a repetition spacer that places fence posts, tile rows or window bays by the diagonal-halving construction 🏗️ instead of by guesswork, reporting each step's foreshortening ratio; an ellipse guide that gives the exact degree of a circle in perspective — asin(minor / major) — and points its minor axis at the right vanishing point, with a cylinder mode showing how the degree opens as a circle moves away from eye level 🧗; and an eye-level planner 🗺️ that shows where the horizon crosses a subject at any camera 📷 height, and can derive the camera 📷 height implied by a scene you already solved.

Then there is practice 🏋️ that is actually graded. The cube drill hands you a solved grid and asks for a box: drag ✋ the seven corners, and every edge is judged on its angular deviation from the vanishing point it should be pointing at, with the depth face checked for proportion. Wrong ❌ edges highlight with their error in degrees, hints reveal one correct construction 🏗️ line at a time ⏱️ for a small score 🔢 cost, and the correct solution can be overlaid on your attempt. Fourteen lessons cover the ground from what a vanishing point really is to where straight-line perspective stops being trustworthy, each with a diagram 📊 you manipulate and a check ✅ you answer by dragging that diagram 📊 into the right state — never by picking from a list 📋. Accuracy stats track your mean edge deviation over time ⏱️, your best and worst axis, ellipse-degree error ❌ and the median residual across every scene you have solved. Everything runs offline 📴, with no account, and Fire Joker makes no sound at all.