Interior Design: How We Model Canal Geometry and Body Proportions for Maximum Experience

With a dildo, the external shape determines the experience. With a pocket pussy or a sex doll torso, the internal structure is what matters. The canal geometry, the texture depth, the wall thickness, the proportions of the body – all of this is invisible, but it is the core of the product. This article opens up the interior design of our products and explains why every decision has a consequence.

Why interior design is a design discipline in its own right

External shape and internal structure follow different logics. A product can look perfect on the outside and be sensorily disappointing on the inside – because canal geometry must be developed based on biomechanical principles, not aesthetic ones.

The central question of interior design is not: How does it look? It is: What happens when pressure, movement, and body heat meet this structure? This is an engineering question, not a design question. And it requires a different process.

→ How we develop external shapes: Anatomical Perfection: How we model lifelike dildos

Part 1: Pocket Pussy – the Science of the Canal

Basic Principle: Pressure, not Friction

The most common misconception in pocket pussy design: More texture means more stimulation. This is not true. Excessive texture creates friction – and friction without sufficient lubricant is uncomfortable, not stimulating.

The correct principle is pressure variation: Alternating constrictions and wider areas in the canal create rhythmic pressure changes that are sensorily much more intense than uniform texture. A well-designed canal stimulates through its geometry – not through the roughness of its surface.

The Five Parameters of Canal Geometry

1. Entry Geometry

The entry is the first point of contact – and it determines the first impression. Too narrow: resistance perceived as uncomfortable. Too wide: no feeling of enclosure. The optimal entry geometry is slightly narrower than the average canal diameter – it creates a defined entry without excessive resistance.

We work with an entry radius of typically 85–90% of the average canal diameter. This value is calibrated individually for each design, depending on the Shore hardness of the material – softer material yields more and requires a narrower initial value.

2. Canal Diameter Progression

A uniform canal diameter is sensorily flat. We work with a progressive progression: The canal starts narrower, widens slightly in the middle, and constricts again at the end. This progression creates a natural pressure progression that structures the experience – beginning, middle, end – without the user having to actively control it.

3. Texture Elements and their Positioning

Texture elements – ribs, nubs, waves – are not distributed evenly across the canal. We position them according to a principle: Stimulation where pressure is most strongly perceived. These are typically the first 4–6 cm of the canal and the area just before the end.

The texture depth is calibrated specifically for the material. For Shore A 15–20 (very soft), 1–2 mm of texture depth is sufficient for a significant sensory effect. For Shore A 25–30, textures must be 2–3 mm deep to produce equivalent stimulation.

4. Wall Thickness and Material Behavior

The wall thickness determines how strongly the canal reacts to pressure. Thin walls (under 8 mm) yield significantly – the experience is soft, but unstructured. Thick walls (over 20 mm) hardly yield – the experience is firm, but not very adaptive.

We work with a wall thickness of 10–15 mm for most designs – enough structure for defined pressure variation, enough flexibility for natural adaptation. These values are simulated for each design before the first mold is built.

5. Canal Depth and Stop Geometry

The end of the canal – the stop – is an often-neglected design element. An abrupt, flat stop creates a hard pressure point. A rounded, slightly conical stop distributes pressure evenly and creates a feeling of depth without uncomfortable resistance.

All our canals have a rounded stop with a radius that is matched to the canal depth. This is a detail that is invisible in the product photo – but immediately noticeable in the experience.

Why Platinum Silicone is Crucial for Canal Geometry

Canal geometry only works if the material retains its shape. TPE deforms under repeated pressure – the canal geometry changes over time, texture elements become flatter, constrictions widen. Platinum silicone retains its geometry permanently. The canal after a hundred uses is geometrically identical to the canal the first time.

→ Why material stability over time is crucial: The Science of Softness: Shore Hardness in Silicone Toys Explained

Part 2: Sex Doll Torso – the Science of Body Proportions

Basic Principle: Proportions before Details

With a sex doll torso, the temptation is great to first think about surface details: skin texture, pigmentation, anatomical subtleties. But the foundation of every convincing torso is the proportions – the ratio of hips to waist, the position of the entry openings, the weight distribution.

A torso with incorrect proportions looks artificial – regardless of how good the surface details are. A torso with correct proportions looks convincing – even if the surface details are simplified.

The Three Proportion Parameters

1. Hip-Waist Ratio and Weight Distribution

The hip-waist ratio determines the visual and haptic persuasiveness of a torso. We work with anatomically validated reference values and calibrate the ratio so that the torso feels natural in the hand – not too wide for comfortable handling, not too narrow for convincing proportions.

Weight distribution is an often-overlooked parameter: Platinum silicone has a density of approximately 1.1–1.2 g/cm³. For a large torso, this means a total weight of several kilograms. We calculate the material distribution so that the center of gravity is natural – the product does not tip over, lies stable, and moves predictably during use.

2. Position and Angle of Entry Openings

The position of the vaginal and anal openings relative to each other and to the body geometry is a precise design parameter. Too close together: anatomically implausible, limited usability. Too far apart: also implausible, unfavorable ergonomics.

We work with anatomical reference values for the distance and calibrate the entry angle so that both openings are optimally accessible in natural use positions. The angle of the vaginal opening is slightly tilted forward – corresponding to the natural anatomical alignment.

3. Surface Geometry and Skin Texture

The surface of a torso must meet two requirements simultaneously: be visually convincing and haptically pleasant. Too much surface detail – deep pores, pronounced skin texture – can feel rough. Too little detail looks artificial.

We work with a micro-texture of 0.1–0.3 mm depth – visible under direct light, but haptically silky. This texture depth is specifically calibrated for platinum silicone: the material fully transfers these fine structures from the mold, while TPE often smooths them out.

Dual-Density in the Torso: When Two Layers Create a Body Sensation

For maximum lifelike realism, we use dual-density construction in selected torso designs: a softer outer shell (Shore A 15–20) over a firmer core (Shore A 30–40). The result is a haptics that is closer to human tissue than any single-stage material.

For the torso, dual-density is particularly relevant for the gluteal region: The soft outer material yields, the firm core provides structure. The result is a feel that is natural to the touch – not like rubber, not like gel, but like tissue.

What Connects Both Product Types: Interior Design as a Quality Promise

Pocket pussies and sex doll torsos are different products with different design priorities. What connects them: The interior is the product. The external form is the context.

A manufacturer who takes interior design seriously documents their canal geometry, calibrates their texture depth specifically for the material, and simulates material behavior before the first casting. A manufacturer who does not do this produces products that look good in photos and disappoint in use.

At SilikonLust, interior design is not an afterthought. It is the starting point.

Read More: The Complete Design World of SilikonLust

• From Sketch to Model: The Design Process of Our Fantasy Toys – the overarching design process
• Anatomical Perfection: How We Model Lifelike Dildos – External Shape and Anatomy
• The Science of Softness: Shore Hardness in Silicone Toys Explained
• What is Platinum Silicone? Material, Manufacturing, and Body Feel
• Pore-free and Hygienic: The Microscopic Truth About Silicone

Frequently Asked Questions

What is canal geometry and why is it important?

Canal geometry refers to the three-dimensional structure of the internal canal of a pocket pussy – diameter progression, texture elements, wall thickness, entry and stop geometry. It determines how pressure, movement, and body heat are perceived in the canal. A well-designed canal geometry stimulates through pressure variation, not friction.

Why does the canal geometry of TPE products change over time?

TPE is not chemically cross-linked – it is physically mixed. Under repeated pressure and body heat, the material structure changes: constrictions widen, texture elements become flatter, and the canal geometry loses its precision. Platinum silicone is chemically cross-linked and retains its geometry permanently.

What is the difference between single-stage and dual-density platinum silicone for torsos?

Single-stage silicone has the same Shore hardness throughout the entire product. Dual-density combines a softer outer shell (Shore A 15–20) with a firmer core (Shore A 30–40). The result is a haptics that is closer to human tissue – a soft surface feel with a structural core.

How deep should texture elements be in a canal?

The optimal texture depth depends on the Shore hardness. For Shore A 15–20, 1–2 mm is sufficient for a significant sensory effect. For Shore A 25–30, 2–3 mm is required. Textures that are too shallow are sensorily invisible; textures that are too deep create friction instead of pressure variation.

Why is the position of the openings on a sex doll torso a design parameter?

The position and angle of the vaginal and anal openings determine the ergonomics in different use positions. Anatomically incorrectly positioned openings limit usability and appear artificial. We calibrate the position and angle according to anatomical reference values for optimal accessibility in natural positions.